Merge pull request #844 from gnembon/expression_optimizer

Expression optimizer

docs/scarpet/api/Overview.md

@@ -1,7 +1,19 @@
 # Minecraft specific API and `scarpet` language add-ons and commands
 
-Here is the gist of the Minecraft related functions. Otherwise the CarpetScript could live without Minecraft.
+Here is the gist of the Minecraft related functions. Otherwise the scarpet could live without Minecraft.
 
+## Global scarpet options
+
+These options affect directly how scarpet functions and can be triggered via `/carpet` command.
+ - `commandScript`: disables `/script` command making it impossible to control apps in game. Apps will still load and run 
+ when loaded with the world (i.e. present in the world/scripts folder)
+ - `scriptsAutoload`: when set to `false` will prevent apps loaded with the world to load automatically. You can still
+ load them on demand via `/script load` command
+ - `commandScriptACE`: command permission level that is used to trigger commands from scarpet scripts (regardless who triggeres
+ the code that calls the command). Defaults to `ops`, could be customized to any level via a numerical value (0, 1, 2, 3 or 4)
+ - `scriptsOptimization`: when disabled, disables default app compile time optimizations. If your app behaves differently with
+ and without optimizations, please file a bug report on the bug tracker and disable code optimizations
+ - `scriptsDebugging`: Puts detailed information about apps loading, performance and runtime in system log.
 
 ## App structure
 

docs/scarpet/language/FunctionsAndControlFlow.md

@@ -2,7 +2,7 @@
 
 ## Writing programs with more than 1 line
 
-### `Operator ;`
+### Operator `;`, `then(...)`
 
 To effectively write programs that have more than one line, a programmer needs way to specify a sequence of commands 
 that execute one after another. In `scarpet` this can be achieved with `;`. Its an operator, and by separating 
@@ -22,7 +22,7 @@ in `scarpet`, and not barely an instruction delimiter, terminating the code with
 be valid. Having said that, since many programming languages don't care about the number of op terminators 
 programmers use, carpet preprocessor will remove all unnecessary semicolons from scripts when compiled.
 
-In general `expr; expr; expr; expr` is equivalent to `(((expr ; expr) ; expr) ; expr)`.
+In general `expr; expr; expr; expr` is equivalent to `(((expr ; expr) ; expr) ; expr)` or `then(expr, expr, expr, expr)`.
 
 Result of the evaluated expression is the same as the result of the second expression, but first expression 
 is also evaluated for side-effects
@@ -132,15 +132,16 @@ foo(... x) -> ...  # all arguments for foo are included in the list
     
 </pre>
 
-### `import(module_name, symbols ...)`
+### `import(module_name, ? symbols ...)`
 
 Imports symbols from other apps and libraries into the current one: global variables or functions, allowing to use 
 them in the current app. This includes other symbols imported by these modules. Scarpet supports circular dependencies, 
 but if symbols are used directly in the module body rather than functions, it may not be able to retrieve them. 
+
 Returns full list of available symbols that could be imported from this module, which can be used to debug import 
 issues, and list contents of libraries.
 
-### `call(function, args.....)`
+### `call(function, ? args ...)`
 
 calls a user defined function with specified arguments. It is equivalent to calling `function(args...)` directly 
 except you can use it with function value, or name instead. This means you can pass functions to other user defined 

docs/scarpet/language/Operators.md

@@ -6,6 +6,12 @@ as `2+(2*2)`, not `(2+2)*2`, otherwise they are applied from left to right, i.e.
 as `(2+4)-3`, which in case of numbers doesn't matter, but since `scarpet` allows for mixing all value types 
 the associativity would matter, and may lead to unintended effects:
 
+Operators can be unary - with one argument prefixed by the operator (like `-`, `!`, `...`), "practically binary" (that
+clearly have left and right operands, like assignment `=` operator), and "technically binary" (all binary operators have left and 
+right hand, but can be frequently chained together, like `1+2+3`). All "technically binary" operators (where chaining makes sense)
+have their functional counterparts, e.g. `1+2+3` is equivalent to `sum(1, 2, 3)`. Functional and operatoral forms are directly 
+equivalent - they actually will result in the same code as scarpet will optimize long operator chains into their optimized functional forms. 
+
 Important operator is function definition `->` operator. It will be covered 
 in [User Defined Functions and Program Control Flow](docs/scarpet/language/FunctionsAndControlFlow.md)
 
@@ -118,7 +124,7 @@ $);
 /script run global_get_enchantment(player(), 'sharpness')
 </pre>
 
-### `Basic Arithmetic Operators + - * /`
+### Basic Arithmetic Operators `+`, `sum(...)`, `-`, `difference(...)`, `*`, `product(...)`, `/`, `quotient(...)`
 
 Allows to add the results of two expressions. If the operands resolve to numbers, the result is arithmetic operation. 
 In case of strings, adding or subtracting from a string results in string concatenation and removal of substrings 
@@ -134,6 +140,9 @@ Addition with maps (`{}` or `m()`) results in a new map with keys from both maps
 adding elements of the right argument to the keys, of left map, or just adding the right value as a new key
 in the output map. 
 
+Functional forms of `-` and `/` have less intuitive multi-nary interpretation, but they might be useful in some situations.
+`x-y-z` resolves to `difference(x, y, z)`.
+
 Examples:
 
 <pre>
@@ -149,7 +158,7 @@ b = [100,63,100]; b+[10,0,10]  => [110,63,110]
 {'a' -> 1} + {'b' -> 2} => {'a' -> 1, 'b' -> 2}
 </pre>
 
-### `Just Operators % ^`
+### Just Operators `%`, `^`
 
 The modulo and exponent (power) operators work only if both operands are numbers
 
@@ -160,11 +169,11 @@ The modulo and exponent (power) operators work only if both operands are numbers
 -3 ^ pi => // Error
 </pre>
 
-### `Comparison Operators == != < > <= >=`
+### Comparison Operators `==`, `equal()`, `!=`, `unique()`, `<`, `increasing()`, `>`, `decreasing()`, `<=`, `nondecreasing()`, `>=`, `nonincreasing()`
 
-Allows to compare the results of two expressions. For numbers it is considers arithmetic order of numbers, for 
+Allows to compare the results of two expressions. For numbers, it considers arithmetic order of numbers, for 
 strings - lexicographical, nulls are always 'less' than everything else, and lists check their elements - 
-if the sizes are different, the size matters, otherwise, pairwise comparisons for each elements are performed. 
+if the sizes are different, the size matters, otherwise, pairwise comparisons for each element are performed. 
 The same order rules than with all these operators are used with the default sortographical order as used by `sort` 
 function. All of these are true:
 
@@ -180,7 +189,12 @@ null < -1000
 3 == 3.0
 </pre>
 
-### `Logical Operators && ||`
+Functional variants of these operators allow to assert certain paradigms on multiple arguments at once. This means that 
+due to formal equivalence `x < y < z` is equivalent to `x < y & y < z` because of direct mapping to `increasing(x, y, z)`. This translates through
+the parentheses, so `((x < y) < z)` is the same as `increasing(x, y, z)`. To achieve the same effect as you would see in other
+ languages (not python), you would need to cast the first pair to boolean value, i.e. `bool(x < y) < z`. 
+
+### Logical Operators `&&`, `and(...)`, `||`, `or(...)`
 
 These operator compute respective boolean operation on the operands. What it important is that if calculating of the 
 second operand is not necessary, it won't be evaluated, which means one can use them as conditional statements. In 

docs/scarpet/resources/editors/idea/1.txt

@@ -3,6 +3,7 @@ acos
 acosh
 acot
 all
+and
 asin
 asinh
 atan
@@ -21,8 +22,11 @@ cot
 coth
 csc
 csch
+decreasing
 deg
 delete
+difference
+equal
 exit
 fact
 filter
@@ -34,6 +38,7 @@ has
 hash_code
 if
 import
+increasing
 join
 keys
 l
@@ -48,14 +53,19 @@ mandelbrot
 map
 max
 min
+nondecreasing
+nonincreasing
 not
 number
+or
 outer
 pairs
 perlin
 print
+product
 profile_expr
 put
+quotient
 rad
 rand
 range
@@ -75,6 +85,7 @@ sleep
 slice
 sort
 sort_key
+sum
 synchronize
 system_variable_get
 system_variable_set
@@ -90,12 +101,14 @@ task_dock
 task_join
 task_thread
 task_value
+then
 throw
 time
 title
 try
 type
 undef
+unique
 upper
 values
 var

docs/scarpet/resources/editors/npp/scarpet.xml

@@ -31,6 +31,7 @@
                 log log10 log1p
                 sqrt
                 max min abs round floor ceil
+                then sum difference product quotient equal unique increasing decreasing nonincreasing nondecreasing or and
                 mandelbrot relu
                 perlin simplex
 

src/main/java/carpet/CarpetSettings.java

@@ -443,6 +443,19 @@ public class CarpetSettings
     )
     public static boolean scriptsAutoload = true;
 
+    @Rule(
+            desc = "Enables scripts debugging messages in system log",
+            category = SCARPET
+    )
+    public static boolean scriptsDebugging = false;
+
+    @Rule(
+            desc = "Enables scripts optimization",
+            category = SCARPET
+    )
+    public static boolean scriptsOptimization = true;
+
+
     @Rule(desc = "Enables /player command to control/spawn players", category = COMMAND)
     public static String commandPlayer = "ops";
 

src/main/java/carpet/commands/ScriptCommand.java

@@ -78,8 +78,8 @@ public class ScriptCommand
         // not that useful in commandline, more so in external scripts, so skipping here
         if (eventPrefix != null) scarpetMatches.addAll(CarpetEventServer.Event.publicEvents(null).stream().
                 filter(e -> e.name.startsWith(eventPrefix)).map(s -> "__on_"+s.name+"(").collect(Collectors.toList()));
-        scarpetMatches.addAll(host.globaFunctionNames(host.main, s -> s.startsWith(prefix)).map(s -> s+"(").collect(Collectors.toList()));
-        scarpetMatches.addAll(host.globaVariableNames(host.main, s -> s.startsWith(prefix)).collect(Collectors.toList()));
+        scarpetMatches.addAll(host.globalFunctionNames(host.main, s -> s.startsWith(prefix)).map(s -> s+"(").collect(Collectors.toList()));
+        scarpetMatches.addAll(host.globalVariableNames(host.main, s -> s.startsWith(prefix)).collect(Collectors.toList()));
         return scarpetMatches;
     }
 
@@ -332,7 +332,7 @@ public class ScriptCommand
     private static Collection<String> suggestFunctionCalls(CommandContext<ServerCommandSource> c) throws CommandSyntaxException
     {
         CarpetScriptHost host = getHost(c);
-        return host.globaFunctionNames(host.main, s ->  !s.startsWith("_")).sorted().collect(Collectors.toList());
+        return host.globalFunctionNames(host.main, s ->  !s.startsWith("_")).sorted().collect(Collectors.toList());
     }
     private static int listEvents(ServerCommandSource source)
     {
@@ -358,7 +358,7 @@ public class ScriptCommand
         ServerCommandSource source = context.getSource();
 
         Messenger.m(source, "lb Stored functions"+((host == CarpetServer.scriptServer.globalHost)?":":" in "+host.getName()+":"));
-        host.globaFunctionNames(host.main, (str) -> all || !str.startsWith("__")).sorted().forEach( (s) -> {
+        host.globalFunctionNames(host.main, (str) -> all || !str.startsWith("__")).sorted().forEach( (s) -> {
             FunctionValue fun = host.getFunction(s);
             if (fun == null)
             {
@@ -379,7 +379,7 @@ public class ScriptCommand
         //Messenger.m(source, "w "+code);
         Messenger.m(source, "w  ");
         Messenger.m(source, "lb Global variables"+((host == CarpetServer.scriptServer.globalHost)?":":" in "+host.getName()+":"));
-        host.globaVariableNames(host.main, (s) -> s.startsWith("global_")).sorted().forEach( (s) -> {
+        host.globalVariableNames(host.main, (s) -> s.startsWith("global_")).sorted().forEach( (s) -> {
             LazyValue variable = host.getGlobalVariable(s);
             if (variable == null)
             {

src/main/java/carpet/script/CarpetScriptHost.java

@@ -498,7 +498,7 @@ public class CarpetScriptHost extends ScriptHost
 
         boolean hasTypeSupport = appConfig.getOrDefault(StringValue.of("legacy_command_type_support"), Value.FALSE).getBoolean();
 
-        for (String function : globaFunctionNames(main, s ->  !s.startsWith("_")).sorted().collect(Collectors.toList()))
+        for (String function : globalFunctionNames(main, s ->  !s.startsWith("_")).sorted().collect(Collectors.toList()))
         {
             if (hasTypeSupport)
             {
@@ -1004,15 +1004,7 @@ public class CarpetScriptHost extends ScriptHost
                 return null;
             }
 
-            String shebang = message;
-            if (expr.module != null)
-            {
-                shebang += " in " + expr.module.getName() + "";
-            }
-            else
-            {
-                shebang += " in system chat";
-            }
+            String shebang = message+" in "+expr.getModuleName();
             if (token != null)
             {
                 String[] lines = expr.getCodeString().split("\n");

src/main/java/carpet/script/CarpetScriptServer.java

@@ -5,6 +5,7 @@ import carpet.script.bundled.BundledModule;
 import carpet.CarpetServer;
 import carpet.script.bundled.FileModule;
 import carpet.script.bundled.Module;
+import carpet.script.exception.IntegrityException;
 import carpet.script.exception.InvalidCallbackException;
 import carpet.script.value.FunctionValue;
 import carpet.script.value.Value;
@@ -403,7 +404,7 @@ public class CarpetScriptServer
             {
                 host.callUDF(BlockPos.ORIGIN, source.withLevel(CarpetSettings.runPermissionLevel), udf, argv);
             }
-            catch (NullPointerException | InvalidCallbackException npe)
+            catch (NullPointerException | InvalidCallbackException | IntegrityException npe)
             {
                 if (reportFails) return -1;
                 continue;

src/main/java/carpet/script/Context.java

@@ -8,17 +8,21 @@ import java.util.Set;
 
 public class Context
 {
-    public static final int NONE = 0;
-    public static final int VOID = 1;
-    public static final int BOOLEAN = 2;
-    public static final int NUMBER = 3;
-    public static final int STRING = 4;
-    public static final int LIST = 5;
-    public static final int ITERATOR = 6;
-    public static final int SIGNATURE = 7;
-    public static final int LOCALIZATION = 8;
-    public static final int LVALUE = 9;
-    public static final int MAPDEF = 10;
+    public enum Type
+    {
+        NONE, VOID, BOOLEAN, NUMBER, STRING, LIST, ITERATOR, SIGNATURE, LOCALIZATION, LVALUE, MAPDEF
+    }
+    public static final Type NONE = Type.NONE;
+    public static final Type VOID = Type.VOID;
+    public static final Type BOOLEAN = Type.BOOLEAN;
+    public static final Type NUMBER = Type.NUMBER;
+    public static final Type STRING = Type.STRING;
+    public static final Type LIST = Type.LIST;
+    public static final Type ITERATOR = Type.ITERATOR;
+    public static final Type SIGNATURE = Type.SIGNATURE;
+    public static final Type LOCALIZATION = Type.LOCALIZATION;
+    public static final Type LVALUE = Type.LVALUE;
+    public static final Type MAPDEF = Type.MAPDEF;
 
     public Map<String, LazyValue> variables = new HashMap<>();
 

src/main/java/carpet/script/Expression.java

@@ -1,5 +1,6 @@
 package carpet.script;
 
+import carpet.CarpetSettings;
 import carpet.script.Fluff.AbstractFunction;
 import carpet.script.Fluff.AbstractLazyFunction;
 import carpet.script.Fluff.AbstractLazyOperator;
@@ -16,6 +17,7 @@ import carpet.script.exception.BreakStatement;
 import carpet.script.exception.ContinueStatement;
 import carpet.script.exception.ExitStatement;
 import carpet.script.exception.ExpressionException;
+import carpet.script.exception.IntegrityException;
 import carpet.script.exception.InternalExpressionException;
 import carpet.script.exception.ResolvedException;
 import carpet.script.exception.ReturnStatement;
@@ -31,6 +33,8 @@ import carpet.script.value.FunctionValue;
 import carpet.script.value.NumericValue;
 import carpet.script.value.StringValue;
 import carpet.script.value.Value;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
 import it.unimi.dsi.fastutil.objects.Object2ObjectOpenHashMap;
 
 import java.math.BigInteger;
@@ -44,6 +48,7 @@ import java.util.Stack;
 import java.util.function.BiFunction;
 import java.util.function.Function;
 import java.util.function.Supplier;
+import java.util.stream.Collectors;
 
 import static java.lang.Math.max;
 import static java.lang.Math.min;
@@ -61,7 +66,7 @@ public class Expression
 
     public String getModuleName()
     {
-        return module == null?null:module.getName();
+        return module == null?"system chat":module.getName();
     }
 
     public void asATextSource()
@@ -85,6 +90,27 @@ public class Expression
     private final Map<String, ILazyFunction> functions = new  Object2ObjectOpenHashMap<>();
     public Set<String> getFunctionNames() {return functions.keySet();}
 
+    private final Map<String, String> functionalEquivalence = new Object2ObjectOpenHashMap<>();
+    public void addFunctionalEquivalence(String operator, String function)
+    {
+        assert operators.containsKey(operator);
+        assert functions.containsKey(function);
+        functionalEquivalence.put(operator, function);
+    }
+
+    private final Map<String, Value> constants = ImmutableMap.of(
+            "euler", Arithmetic.euler,
+            "pi", Arithmetic.PI,
+            "null", Value.NULL,
+            "true", Value.TRUE,
+            "false", Value.FALSE
+    );
+
+    protected Value getConstantFor(String surface)
+    {
+        return constants.get(surface);
+    }
+
     public List<String> getExpressionSnippet(Tokenizer.Token token)
     {
         String code = this.getCodeString();
@@ -138,13 +164,28 @@ public class Expression
     }
 
 
-    public void addLazyUnaryOperator(String surface, int precedence, boolean leftAssoc,
-                                       TriFunction<Context, Integer, LazyValue, LazyValue> lazyfun)
+    public void addLazyUnaryOperator(String surface, int precedence, boolean leftAssoc, boolean pure, Function<Context.Type,Context.Type> staticTyper,
+                                       TriFunction<Context, Context.Type, LazyValue, LazyValue> lazyfun)
     {
         operators.put(surface+"u", new AbstractLazyOperator(precedence, leftAssoc)
         {
             @Override
-            public LazyValue lazyEval(Context c, Integer t, Expression e, Tokenizer.Token token, LazyValue v, LazyValue v2)
+            public boolean pure() {
+                return pure;
+            }
+
+            @Override
+            public boolean transitive() {
+                return false;
+            }
+
+            @Override
+            public Context.Type staticType(Context.Type outerType) {
+                return staticTyper.apply(outerType);
+            }
+
+            @Override
+            public LazyValue lazyEval(Context c, Context.Type t, Expression e, Tokenizer.Token token, LazyValue v, LazyValue v2)
             {
                 try
                 {
@@ -159,13 +200,23 @@ public class Expression
     }
 
 
-    public void addLazyBinaryOperatorWithDelegation(String surface, int precedence, boolean leftAssoc,
-                                       SexFunction<Context, Integer, Expression, Tokenizer.Token, LazyValue, LazyValue, LazyValue> lazyfun)
+    public void addLazyBinaryOperatorWithDelegation(String surface, int precedence, boolean leftAssoc, boolean pure,
+                                       SexFunction<Context, Context.Type, Expression, Tokenizer.Token, LazyValue, LazyValue, LazyValue> lazyfun)
     {
         operators.put(surface, new AbstractLazyOperator(precedence, leftAssoc)
         {
             @Override
-            public LazyValue lazyEval(Context c, Integer type, Expression e, Tokenizer.Token t, LazyValue v1, LazyValue v2)
+            public boolean pure() {
+                return pure;
+            }
+
+            @Override
+            public boolean transitive() {
+                return false;
+            }
+
+            @Override
+            public LazyValue lazyEval(Context c, Context.Type type, Expression e, Tokenizer.Token t, LazyValue v1, LazyValue v2)
             {
                 try
                 {
@@ -179,13 +230,28 @@ public class Expression
         });
     }
 
-    public void addLazyFunctionWithDelegation(String name, int numpar,
-                                                     QuinnFunction<Context, Integer, Expression, Tokenizer.Token, List<LazyValue>, LazyValue> lazyfun)
+    public void addCustomFunction(String name, ILazyFunction fun)
+    {
+        functions.put(name, fun);
+    }
+
+    public void addLazyFunctionWithDelegation(String name, int numpar, boolean pure, boolean transitive,
+                                                     QuinnFunction<Context, Context.Type, Expression, Tokenizer.Token, List<LazyValue>, LazyValue> lazyfun)
     {
         functions.put(name, new AbstractLazyFunction(numpar, name)
         {
             @Override
-            public LazyValue lazyEval(Context c, Integer type, Expression e, Tokenizer.Token t, List<LazyValue> lv)
+            public boolean pure() {
+                return pure;
+            }
+
+            @Override
+            public boolean transitive() {
+                return transitive;
+            }
+
+            @Override
+            public LazyValue lazyEval(Context c, Context.Type type, Expression e, Tokenizer.Token t, List<LazyValue> lv)
             {
                 ILazyFunction.checkInterrupts();
                 try
@@ -200,13 +266,23 @@ public class Expression
         });
     }
 
-    public void addFunctionWithDelegation(String name, int numpar,
-                                              QuinnFunction<Context, Integer, Expression, Tokenizer.Token, List<Value>, Value> fun)
+    public void addFunctionWithDelegation(String name, int numpar, boolean pure, boolean transitive,
+                                              QuinnFunction<Context, Context.Type, Expression, Tokenizer.Token, List<Value>, Value> fun)
     {
         functions.put(name, new AbstractLazyFunction(numpar, name)
         {
             @Override
-            public LazyValue lazyEval(Context c, Integer type, Expression e, Tokenizer.Token t, List<LazyValue> lv)
+            public boolean pure() {
+                return pure;
+            }
+
+            @Override
+            public boolean transitive() {
+                return transitive;
+            }
+
+            @Override
+            public LazyValue lazyEval(Context c, Context.Type type, Expression e, Tokenizer.Token t, List<LazyValue> lv)
             {
                 try
                 {
@@ -221,13 +297,30 @@ public class Expression
         });
     }
 
-    public void addLazyBinaryOperator(String surface, int precedence, boolean leftAssoc,
-                                       QuadFunction<Context, Integer, LazyValue, LazyValue, LazyValue> lazyfun)
+    public void addLazyBinaryOperator(String surface, int precedence, boolean leftAssoc, boolean pure, Function<Context.Type, Context.Type> typer,
+                                       QuadFunction<Context, Context.Type, LazyValue, LazyValue, LazyValue> lazyfun)
     {
         operators.put(surface, new AbstractLazyOperator(precedence, leftAssoc)
         {
+
             @Override
-            public LazyValue lazyEval(Context c, Integer t, Expression e, Tokenizer.Token token, LazyValue v1, LazyValue v2)
+            public boolean pure() {
+                return pure;
+            }
+
+            @Override
+            public boolean transitive() {
+                return false;
+            }
+
+            @Override
+            public Context.Type staticType(Context.Type outerType)
+            {
+                return typer.apply(outerType);
+            }
+
+            @Override
+            public LazyValue lazyEval(Context c, Context.Type t, Expression e, Tokenizer.Token token, LazyValue v1, LazyValue v2)
             {
                 ILazyFunction.checkInterrupts();
                 try
@@ -242,13 +335,23 @@ public class Expression
         });
     }
 
-    public void addBinaryContextOperator(String surface, int precedence, boolean leftAssoc,
-                                      QuadFunction<Context, Integer, Value, Value, Value> fun)
+    public void addBinaryContextOperator(String surface, int precedence, boolean leftAssoc, boolean pure, boolean transitive,
+                                      QuadFunction<Context, Context.Type, Value, Value, Value> fun)
     {
         operators.put(surface, new AbstractLazyOperator(precedence, leftAssoc)
         {
             @Override
-            public LazyValue lazyEval(Context c, Integer t, Expression e, Tokenizer.Token token, LazyValue v1, LazyValue v2)
+            public boolean pure() {
+                return pure;
+            }
+
+            @Override
+            public boolean transitive() {
+                return transitive;
+            }
+
+            @Override
+            public LazyValue lazyEval(Context c, Context.Type t, Expression e, Tokenizer.Token token, LazyValue v1, LazyValue v2)
             {
                 try
                 {
@@ -267,6 +370,8 @@ public class Expression
     {
         if (exc instanceof ExitStatement)
             return exc;
+        if (exc instanceof IntegrityException)
+            return exc;
         if (exc instanceof InternalExpressionException)
             return ((InternalExpressionException) exc).promote(c, e, token);
         if (exc instanceof ArithmeticException)
@@ -309,6 +414,20 @@ public class Expression
         });
     }
 
+    public void addImpureUnaryFunction(String name, Function<Value, Value> fun)
+    {
+        functions.put(name,  new AbstractFunction(1, name)
+        {
+            @Override
+            public boolean pure() {
+                return false;
+            }
+
+            @Override
+            public Value eval(List<Value> parameters) { return fun.apply(parameters.get(0)); }
+        });
+    }
+
     public void addBinaryFunction(String name, BiFunction<Value, Value, Value> fun)
     {
         functions.put(name, new AbstractFunction(2, name)
@@ -327,6 +446,20 @@ public class Expression
         });
     }
 
+    public void addImpureFunction(String name, Function<List<Value>, Value> fun)
+    {
+        functions.put(name, new AbstractFunction(-1, name)
+        {
+            @Override
+            public boolean pure() {
+                return false;
+            }
+
+            @Override
+            public Value eval(List<Value> parameters) { return fun.apply(parameters); }
+        });
+    }
+
     public void addMathematicalUnaryFunction(String name, Function<Double, Double> fun)
     {
         addUnaryFunction(name, (v) -> new NumericValue(fun.apply(NumericValue.asNumber(v).getDouble())));
@@ -344,12 +477,22 @@ public class Expression
     }
 
 
-    public void addLazyFunction(String name, int num_params, TriFunction<Context, Integer, List<LazyValue>, LazyValue> fun)
+    public void addLazyFunction(String name, int num_params, TriFunction<Context, Context.Type, List<LazyValue>, LazyValue> fun)
     {
         functions.put(name, new AbstractLazyFunction(num_params, name)
         {
             @Override
-            public LazyValue lazyEval(Context c, Integer i, Expression e, Tokenizer.Token t, List<LazyValue> lazyParams)
+            public boolean pure() {
+                return false;
+            }
+
+            @Override
+            public boolean transitive() {
+                return false;
+            }
+
+            @Override
+            public LazyValue lazyEval(Context c, Context.Type i, Expression e, Tokenizer.Token t, List<LazyValue> lazyParams)
             {
                 ILazyFunction.checkInterrupts();
                 try
@@ -364,12 +507,58 @@ public class Expression
         });
     }
 
-    public void addContextFunction(String name, int num_params, TriFunction<Context, Integer, List<Value>, Value> fun)
+    public void addPureLazyFunction(String name, int num_params, Function<Context.Type, Context.Type> typer, TriFunction<Context, Context.Type, List<LazyValue>, LazyValue> fun)
     {
         functions.put(name, new AbstractLazyFunction(num_params, name)
         {
             @Override
-            public LazyValue lazyEval(Context c, Integer i, Expression e, Tokenizer.Token t, List<LazyValue> lazyParams)
+            public boolean pure() {
+                return true;
+            }
+
+            @Override
+            public boolean transitive() {
+                return false;
+            }
+
+            @Override
+            public Context.Type staticType(Context.Type outerType)
+            {
+                return typer.apply(outerType);
+            }
+
+            @Override
+            public LazyValue lazyEval(Context c, Context.Type i, Expression e, Tokenizer.Token t, List<LazyValue> lazyParams)
+            {
+                ILazyFunction.checkInterrupts();
+                try
+                {
+                    return fun.apply(c, i, lazyParams);
+                }
+                catch (RuntimeException exc)
+                {
+                    throw handleCodeException(c, exc, e, t);
+                }
+            }
+        });
+    }
+
+    public void addContextFunction(String name, int num_params, TriFunction<Context, Context.Type, List<Value>, Value> fun)
+    {
+        functions.put(name, new AbstractLazyFunction(num_params, name)
+        {
+            @Override
+            public boolean pure() {
+                return false;
+            }
+
+            @Override
+            public boolean transitive() {
+                return false;
+            }
+
+            @Override
+            public LazyValue lazyEval(Context c, Context.Type i, Expression e, Tokenizer.Token t, List<LazyValue> lazyParams)
             {
                 ILazyFunction.checkInterrupts();
                 try
@@ -385,12 +574,27 @@ public class Expression
         });
     }
 
-    public void addTypedContextFunction(String name, int num_params, int reqType, TriFunction<Context, Integer, List<Value>, Value> fun)
+    public void addTypedContextFunction(String name, int num_params, Context.Type reqType, TriFunction<Context, Context.Type, List<Value>, Value> fun)
     {
         functions.put(name, new AbstractLazyFunction(num_params, name)
         {
             @Override
-            public LazyValue lazyEval(Context c, Integer i, Expression e, Tokenizer.Token t, List<LazyValue> lazyParams)
+            public boolean pure() {
+                return true;
+            }
+
+            @Override
+            public boolean transitive() {
+                return false;
+            }
+
+            @Override
+            public Context.Type staticType(Context.Type outerType) {
+                return reqType;
+            }
+
+            @Override
+            public LazyValue lazyEval(Context c, Context.Type i, Expression e, Tokenizer.Token t, List<LazyValue> lazyParams)
             {
                 try
                 {
@@ -448,7 +652,22 @@ public class Expression
             }
 
             @Override
-            public LazyValue lazyEval(Context c, Integer type, Expression expr, Tokenizer.Token token, List<LazyValue> lazyParams)
+            public boolean pure() {
+                return originalFunction.pure();
+            }
+
+            @Override
+            public boolean transitive() {
+                return originalFunction.transitive();
+            }
+
+            @Override
+            public Context.Type staticType(Context.Type outerType) {
+                return originalFunction.staticType(outerType);
+            }
+
+            @Override
+            public LazyValue lazyEval(Context c, Context.Type type, Expression expr, Tokenizer.Token token, List<LazyValue> lazyParams)
             {
                 c.host.issueDeprecation(copy+"(...)");
                 return originalFunction.lazyEval(c, type, expr, token, lazyParams);
@@ -471,7 +690,7 @@ public class Expression
 
     public LazyValue getOrSetAnyVariable(Context c, String name)
     {
-        LazyValue var = null;
+        LazyValue var;
         if (!name.startsWith("global_"))
         {
             var = c.getVariable(name);
@@ -596,16 +815,16 @@ public class Expression
                 case OPEN_PAREN:
                     if (previousToken != null)
                     {
-                        if (previousToken.type == Tokenizer.Token.TokenType.LITERAL || previousToken.type == Tokenizer.Token.TokenType.CLOSE_PAREN
-                                || previousToken.type == Tokenizer.Token.TokenType.VARIABLE
-                                || previousToken.type == Tokenizer.Token.TokenType.HEX_LITERAL)
-                        {
+                        //if (previousToken.type == Tokenizer.Token.TokenType.LITERAL || previousToken.type == Tokenizer.Token.TokenType.CLOSE_PAREN
+                        //        || previousToken.type == Tokenizer.Token.TokenType.VARIABLE
+                        //        || previousToken.type == Tokenizer.Token.TokenType.HEX_LITERAL)
+                        //{
                             // Implicit multiplication, e.g. 23(a+b) or (a+b)(a-b)
-                            Tokenizer.Token multiplication = new Tokenizer.Token();
-                            multiplication.append("*");
-                            multiplication.type = Tokenizer.Token.TokenType.OPERATOR;
-                            stack.push(multiplication);
-                        }
+                        //    Tokenizer.Token multiplication = new Tokenizer.Token();
+                        //    multiplication.append("*");
+                        //    multiplication.type = Tokenizer.Token.TokenType.OPERATOR;
+                        //    stack.push(multiplication);
+                        //}
                         // if the ( is preceded by a valid function, then it
                         // denotes the start of a parameter list
                         if (previousToken.type == Tokenizer.Token.TokenType.FUNCTION)
@@ -672,19 +891,15 @@ public class Expression
     }
 
     public Value eval(Context c)
-    {
-        return eval(c, Context.NONE);
-    }
-    public Value eval(Context c, Integer expectedType)
     {
         if (ast == null)
         {
             ast = getAST(c);
         }
-        return evalValue(() -> ast, c, expectedType);
+        return evalValue(() -> ast, c, Context.Type.NONE);
     }
 
-    public Value evalValue(Supplier<LazyValue> exprProvider, Context c, Integer expectedType)
+    public Value evalValue(Supplier<LazyValue> exprProvider, Context c, Context.Type expectedType)
     {
         try
         {
@@ -712,35 +927,67 @@ public class Expression
         }
     }
 
-    private LazyValue getAST(Context context)
+    public static class ExpressionNode
     {
-        Stack<LazyValue> stack = new Stack<>();
-        List<Tokenizer.Token> rpn = shuntingYard(context);
-        validate(context, rpn);
-        for (final Tokenizer.Token token : rpn)
+        public LazyValue op;
+        public List<ExpressionNode> args;
+        public Tokenizer.Token token;
+        public List<Tokenizer.Token> range;
+        /**
+         * The Value representation of the left parenthesis, used for parsing
+         * varying numbers of function parameters.
+         */
+        public static final ExpressionNode PARAMS_START = new ExpressionNode(null, null, Tokenizer.Token.NONE);
+        public ExpressionNode(LazyValue op, List<ExpressionNode> args, Tokenizer.Token token)
+        {
+            this.op = op;
+            this.args = args;
+            this.token = token;
+            range = new ArrayList<>();
+            range.add(token);
+        }
+        public static ExpressionNode ofConstant(Value val, Tokenizer.Token token)
+        {
+            return new ExpressionNode(new LazyValue.Constant(val), Collections.emptyList(), token);
+        }
+    }
+
+
+    private ExpressionNode RPNToParseTree(List<Tokenizer.Token> tokens, Context context)
+    {
+        Stack<ExpressionNode> nodeStack = new Stack<>();
+        for (final Tokenizer.Token token : tokens)
         {
             switch (token.type)
             {
                 case UNARY_OPERATOR:
                 {
-                    final LazyValue value = stack.pop();
-                    LazyValue result = (c, t) -> operators.get(token.surface).lazyEval(c, t, this, token, value, null).evalValue(c, t);
-                    stack.push(result);
+                    final ExpressionNode node = nodeStack.pop();
+                    LazyValue result = (c, t) -> operators.get(token.surface).lazyEval(c, t, this, token, node.op, null).evalValue(c, t);
+                    nodeStack.push(new ExpressionNode(result, Collections.singletonList(node), token));
                     break;
                 }
                 case OPERATOR:
-                    final LazyValue v1 = stack.pop();
-                    final LazyValue v2 = stack.pop();
-                    LazyValue result = (c,t) -> operators.get(token.surface).lazyEval(c, t,this, token, v2, v1).evalValue(c, t);
-                    stack.push(result);
+                    final ExpressionNode v1 = nodeStack.pop();
+                    final ExpressionNode v2 = nodeStack.pop();
+                    LazyValue result = (c,t) -> operators.get(token.surface).lazyEval(c, t,this, token, v2.op, v1.op).evalValue(c, t);
+                    nodeStack.push(new ExpressionNode(result, ImmutableList.of(v2, v1), token ));
                     break;
                 case VARIABLE:
-                    stack.push((c, t) -> getOrSetAnyVariable(c, token.surface).evalValue(c, t));
+                    Value constant = getConstantFor(token.surface);
+                    if (constant != null)
+                    {
+                        token.morph(Tokenizer.Token.TokenType.CONSTANT, token.surface);
+                        nodeStack.push(new ExpressionNode(LazyValue.ofConstant(constant), Collections.emptyList(), token));
+                    }
+                    else {
+                        nodeStack.push(new ExpressionNode(((c, t) -> getOrSetAnyVariable(c, token.surface).evalValue(c, t)), Collections.emptyList(), token));
+                    }
                     break;
                 case FUNCTION:
                     String name = token.surface;
                     ILazyFunction f;
-                    ArrayList<LazyValue> p;
+                    ArrayList<ExpressionNode> p;
                     boolean isKnown = functions.containsKey(name); // globals will be evaluated lazily, not at compile time via .
                     if (isKnown)
                     {
@@ -754,47 +1001,301 @@ public class Expression
                     }
                     // pop parameters off the stack until we hit the start of
                     // this function's parameter list
-                    while (!stack.isEmpty() && stack.peek() != LazyValue.PARAMS_START)
+                    while (!nodeStack.isEmpty() && nodeStack.peek() != ExpressionNode.PARAMS_START)
                     {
-                        p.add(stack.pop());
+                        p.add(nodeStack.pop());
+                    }
+                    if (!isKnown)
+                    {
+                        p.add(ExpressionNode.ofConstant(new StringValue(name), token.morphedInto(Tokenizer.Token.TokenType.STRINGPARAM, token.surface)));
+                        token.morph(Tokenizer.Token.TokenType.FUNCTION, "call");
                     }
-                    if (!isKnown) p.add( (c, t) -> new StringValue(name));
                     Collections.reverse(p);
 
-                    if (stack.peek() == LazyValue.PARAMS_START)
+                    if (nodeStack.peek() == ExpressionNode.PARAMS_START)
                     {
-                        stack.pop();
-                    }
+                        nodeStack.pop();
+                    };
+                    List<LazyValue> params = p.stream().map(n -> n.op).collect(Collectors.toList());
 
-                    stack.push((c, t) -> f.lazyEval(c, t, this, token, p).evalValue(c, t));
+                    nodeStack.push(new ExpressionNode(
+                            (c, t) -> f.lazyEval(c, t, this, token, params).evalValue(c, t),
+                            p,token
+                    ));
                     break;
                 case OPEN_PAREN:
-                    stack.push(LazyValue.PARAMS_START);
+                    nodeStack.push(ExpressionNode.PARAMS_START);
                     break;
                 case LITERAL:
-                    stack.push((c, t) ->
+                    Value number;
+                    try
                     {
-                        try
-                        {
-                            return new NumericValue(token.surface);
-                        }
-                        catch (NumberFormatException exception)
-                        {
-                            throw new ExpressionException(c, this, token, "Not a number");
-                        }
-                    });
+                        number = new NumericValue(token.surface);
+                    }
+                    catch (NumberFormatException exception)
+                    {
+                        throw new ExpressionException(context, this, token, "Not a number");
+                    }
+                    token.morph(Tokenizer.Token.TokenType.CONSTANT, token.surface);
+                    nodeStack.push(ExpressionNode.ofConstant(number, token));
                     break;
                 case STRINGPARAM:
-                    stack.push((c, t) -> new StringValue(token.surface) ); // was originally null
+                    token.morph(Tokenizer.Token.TokenType.CONSTANT, token.surface);
+                    nodeStack.push(ExpressionNode.ofConstant(new StringValue(token.surface), token));
                     break;
                 case HEX_LITERAL:
-                    stack.push((c, t) -> new NumericValue(new BigInteger(token.surface.substring(2), 16).doubleValue()));
+                    Value hexNumber;
+                    try
+                    {
+                        hexNumber = new NumericValue(new BigInteger(token.surface.substring(2), 16).longValue());
+                    }
+                    catch (NumberFormatException exception)
+                    {
+                        throw new ExpressionException(context, this, token, "Not a number");
+                    }
+                    token.morph(Tokenizer.Token.TokenType.CONSTANT, token.surface);
+                    nodeStack.push(ExpressionNode.ofConstant(hexNumber, token));
                     break;
                 default:
                     throw new ExpressionException(context, this, token, "Unexpected token '" + token.surface + "'");
             }
         }
-        return stack.pop();
+        return nodeStack.pop();
+    }
+
+    private LazyValue getAST(Context context)
+    {
+        //Stack<LazyValue> stack = new Stack<>();
+        List<Tokenizer.Token> rpn = shuntingYard(context);
+        validate(context, rpn);
+        ExpressionNode root = RPNToParseTree(rpn, context);
+        if (!CarpetSettings.scriptsOptimization)
+            return root.op;
+
+        CarpetScriptServer.LOG.info("Input code size for "+getModuleName()+": " + treeSize(root) + " nodes, " + treeDepth(root) + " deep");
+
+        boolean changed = true;
+        while(changed) {
+            changed = false;
+            while (true) {
+                int tree_size = treeSize(root);
+                int tree_depth = treeDepth(root);
+                boolean optimized = compactTree(root, Context.Type.NONE, 0);
+                if (!optimized) break;
+                changed = true;
+                CarpetScriptServer.LOG.info("Compacted from " + tree_size + " nodes, " + tree_depth + " code depth to " + treeSize(root) + " nodes, " + treeDepth(root) + " code depth");
+            }
+            while (true) {
+                int tree_size = treeSize(root);
+                int tree_depth = treeDepth(root);
+                boolean optimized = optimizeTree(context, root, Context.Type.NONE, 0);
+                if (!optimized) break;
+                changed = true;
+                CarpetScriptServer.LOG.info("Optimized from " + tree_size + " nodes, " + tree_depth + " code depth to " + treeSize(root) + " nodes, " + treeDepth(root) + " code depth");
+            }
+        }
+        return extractOp(context, root, Context.Type.NONE);
+    }
+
+    private int treeSize(ExpressionNode node)
+    {
+        if (node.op instanceof LazyValue.ContextFreeLazyValue) return 1;
+        return node.args.stream().mapToInt(this::treeSize).sum()+1;
+    }
+    private int treeDepth(ExpressionNode node)
+    {
+        if (node.op instanceof LazyValue.ContextFreeLazyValue) return 1;
+        return node.args.stream().mapToInt(this::treeDepth).max().orElse(0)+1;
+    }
+
+
+    private boolean compactTree(ExpressionNode node, Context.Type expectedType, int indent) {
+        // ctx is just to report errors, not values evaluation
+        boolean optimized = false;
+        Tokenizer.Token.TokenType token = node.token.type;
+        if (!token.isFunctional()) return false;
+        // input special cases here, like function signature
+        if (node.op instanceof LazyValue.Constant) return false; // optimized already
+        // function or operator
+        String symbol = node.token.surface;
+        Fluff.EvalNode operation = ((token == Tokenizer.Token.TokenType.FUNCTION) ? functions : operators).get(symbol);
+        Context.Type requestedType = operation.staticType(expectedType);
+        for (ExpressionNode arg : node.args) {
+            if (compactTree(arg, requestedType, indent+1)) optimized = true;
+        }
+
+        if (expectedType != Context.Type.MAPDEF && symbol.equals("->") && node.args.size() == 2) {
+            String rop = node.args.get(1).token.surface;
+            ExpressionNode returnNode = null;
+            if ((rop.equals(";") || rop.equals("then"))) {
+                List<ExpressionNode> thenArgs = node.args.get(1).args;
+                if (thenArgs.size() > 1 && thenArgs.get(thenArgs.size() - 1).token.surface.equals("return")) {
+                    returnNode = thenArgs.get(thenArgs.size() - 1);
+                }
+            } else if (rop.equals("return")) {
+                returnNode = node.args.get(1);
+            }
+            if (returnNode != null) // tail return
+            {
+                if (returnNode.args.size() > 0) {
+                    returnNode.op = returnNode.args.get(0).op;
+                    returnNode.token = returnNode.args.get(0).token;
+                    returnNode.range = returnNode.args.get(0).range;
+                    returnNode.args = returnNode.args.get(0).args;
+                    if (CarpetSettings.scriptsDebugging)
+                        CarpetScriptServer.LOG.info(" - Removed unnecessary tail return of " + returnNode.token.surface + " from function body at line " + (returnNode.token.lineno + 1) + ", node depth " + indent);
+
+                } else {
+                    returnNode.op = LazyValue.ofConstant(Value.NULL);
+                    returnNode.token.morph(Tokenizer.Token.TokenType.CONSTANT, "");
+                    returnNode.args = Collections.emptyList();
+                    if (CarpetSettings.scriptsDebugging)
+                        CarpetScriptServer.LOG.info(" - Removed unnecessary tail return from function body at line " + (returnNode.token.lineno + 1) + ", node depth " + indent);
+
+                }
+
+            }
+        }
+        for (Map.Entry<String, String> pair : functionalEquivalence.entrySet()) {
+            String operator = pair.getKey();
+            String function = pair.getValue();
+            if (symbol.equals(operator) || symbol.equals(function)) {
+                List<ExpressionNode> newargs = new ArrayList<>();
+                boolean contracted = false;
+                for (ExpressionNode arg : node.args) {
+                    String argsymbol = arg.token.surface; // child is unoptimized and also same class
+                    if ((argsymbol.equals(operator) || argsymbol.equals(function)) && (!(arg.op instanceof LazyValue.ContextFreeLazyValue))) {
+                        newargs.addAll(arg.args);
+                        contracted = true;
+                    } else {
+                        newargs.add(arg);
+                    }
+                }
+                if (contracted) {
+                    optimized = true;
+                    if (CarpetSettings.scriptsDebugging)
+                        CarpetScriptServer.LOG.info(" - " + symbol + "(" + node.args.size() + ") => " + function + "(" + newargs.size() + ") at line " + (node.token.lineno + 1) + ", node depth " + indent);
+                    node.token.morph(Tokenizer.Token.TokenType.FUNCTION, function);
+                    node.args = newargs;
+                }
+            }
+        }
+        return optimized;
+    }
+
+    private boolean optimizeTree(Context ctx, ExpressionNode node, Context.Type expectedType, int indent) {
+        // ctx is just to report errors, not values evaluation
+        boolean optimized = false;
+        Tokenizer.Token.TokenType token = node.token.type;
+        if (!token.isFunctional()) return false;
+        String symbol = node.token.surface;
+
+        // input special cases here, like function signature
+        if (node.op instanceof LazyValue.Constant) return false; // optimized already
+        // function or operator
+
+        Fluff.EvalNode operation = ((token == Tokenizer.Token.TokenType.FUNCTION) ? functions : operators).get(symbol);
+        Context.Type requestedType = operation.staticType(expectedType);
+        for (ExpressionNode arg : node.args) {
+            if (optimizeTree(ctx, arg, requestedType, indent+1)) optimized = true;
+        }
+
+        for (ExpressionNode arg : node.args) {
+            if (arg.token.type.isConstant()) continue;
+            if (arg.op instanceof LazyValue.ContextFreeLazyValue) continue;
+            return optimized;
+        }
+        if (!operation.pure())
+        {
+            if (symbol.equals("->") && expectedType == Context.Type.MAPDEF)
+            {
+
+            }
+            else {
+                return optimized;
+            }
+        }
+        List<LazyValue> args = new ArrayList<>(node.args.size());
+        for (ExpressionNode arg : node.args) {
+            try {
+                if (arg.op instanceof LazyValue.Constant) {
+                    Value val = ((LazyValue.Constant) arg.op).get();
+                    args.add((c, t) -> val);
+                }
+                else args.add((c, t) -> arg.op.evalValue(null, requestedType));
+            } catch (NullPointerException npe) {
+                throw new ExpressionException(ctx, this, node.token, "Attempted to evaluate context free expression");
+            }
+        }
+        // applying argument unpacking
+        args= AbstractLazyFunction.lazify(AbstractLazyFunction.unpackLazy(args, null, requestedType));
+        Value result;
+        if (operation instanceof ILazyFunction)
+        {
+            result = ((ILazyFunction) operation).lazyEval(null, expectedType, this, node.token, args).evalValue(null, expectedType);
+        }
+        else if (args.size() == 1)
+        {
+            result = ((ILazyOperator)operation).lazyEval(null, expectedType, this, node.token, args.get(0), null).evalValue(null, expectedType);
+        }
+        else // args == 2
+        {
+            result = ((ILazyOperator)operation).lazyEval(null, expectedType, this, node.token, args.get(0), args.get(1)).evalValue(null, expectedType);
+        }
+        node.op = LazyValue.ofConstant(result);
+        //node.token.morph(Tokenizer.Token.TokenType.CONSTANT, node.token.surface);
+        if (CarpetSettings.scriptsDebugging)
+            CarpetScriptServer.LOG.info(" - "+symbol+"("+args.stream().map(a -> a.evalValue(null, requestedType).getString()).collect(Collectors.joining(", "))+") => "+result.getString()+" at line "+(node.token.lineno+1) +", node depth "+indent);
+        return true;
+    }
+
+    private LazyValue extractOp(Context ctx, ExpressionNode node, Context.Type expectedType)
+    {
+        if (node.op instanceof LazyValue.Constant)
+        {
+            // constants are immutable
+            if (node.token.type.isConstant())
+            {
+                Value value = ((LazyValue.Constant) node.op).get();
+                return (c, t) -> value;
+            }
+            return node.op;
+        }
+        if (node.op instanceof LazyValue.ContextFreeLazyValue)
+        {
+            Value ret = ((LazyValue.ContextFreeLazyValue) node.op).evalType(expectedType);
+            return (c, t) -> ret;
+        }
+        Tokenizer.Token token = node.token;
+        switch (token.type)
+        {
+            case UNARY_OPERATOR: {
+                ILazyOperator op = operators.get(token.surface);
+                Context.Type requestedType = op.staticType(expectedType);
+                LazyValue arg = extractOp(ctx, node.args.get(0), requestedType);
+                return (c, t) -> op.lazyEval(c, t, this, token, arg, null).evalValue(c, t);
+            }
+            case OPERATOR: {
+                ILazyOperator op = operators.get(token.surface);
+                Context.Type requestedType = op.staticType(expectedType);
+                LazyValue arg = extractOp(ctx, node.args.get(0), requestedType);
+                LazyValue arh = extractOp(ctx, node.args.get(1), requestedType);
+                return (c, t) -> op.lazyEval(c, t, this, token, arg, arh).evalValue(c, t);
+            }
+            case VARIABLE:
+                return (c, t) -> getOrSetAnyVariable(c, token.surface).evalValue(c, t);
+            case FUNCTION: {
+                ILazyFunction f = functions.get(token.surface);
+                Context.Type requestedType = f.staticType(expectedType);
+                List<LazyValue> params = node.args.stream().map(n -> extractOp(ctx, n, requestedType)).collect(Collectors.toList());
+                return (c, t) -> f.lazyEval(c, t, this, token, params).evalValue(c, t);
+            }
+            case CONSTANT:
+                return node.op;
+            default:
+                throw new ExpressionException(ctx, this, node.token, "Unexpected token '" + node.token.type +" "+node.token.surface + "'");
+
+        }
     }
 
     private void validate(Context c, List<Tokenizer.Token> rpn)

src/main/java/carpet/script/Fluff.java

@@ -30,13 +30,33 @@ public abstract class Fluff
     @FunctionalInterface
     public interface SexFunction<A, B, C, D, E, F, R> { R apply(A a, B b, C c, D d, E e, F f);}
 
-    public interface ILazyFunction
+    public interface EvalNode
+    {
+        /**
+         * @return true if function has constant output if arguments are constant and can be evaluated
+         * statically (without context)
+         */
+        boolean pure();
+
+        /**
+         * @return true if function has constant output if arguments are constant and can be evaluated
+         * statically (without context)
+         */
+        boolean transitive();
+
+        /**
+         * @return required argument eval type in case its evaluated statically without context but with a given context type
+         */
+        default Context.Type staticType(Context.Type outerType) {return transitive()?outerType:Context.NONE;};
+    }
+
+    public interface ILazyFunction extends EvalNode
     {
         int getNumParams();
 
         boolean numParamsVaries();
 
-        LazyValue lazyEval(Context c, Integer type, Expression expr, Tokenizer.Token token, List<LazyValue> lazyParams);
+        LazyValue lazyEval(Context c, Context.Type type, Expression expr, Tokenizer.Token token, List<LazyValue> lazyParams);
 
         static void checkInterrupts()
         {
@@ -51,13 +71,13 @@ public abstract class Fluff
         Value eval(List<Value> parameters);
     }
 
-    public interface ILazyOperator
+    public interface ILazyOperator extends EvalNode
     {
         int getPrecedence();
 
         boolean isLeftAssoc();
 
-        LazyValue lazyEval(Context c, Integer type, Expression e, Tokenizer.Token t, LazyValue v1, LazyValue v2);
+        LazyValue lazyEval(Context c, Context.Type type, Expression e, Tokenizer.Token t, LazyValue v1, LazyValue v2);
     }
 
     public interface IOperator extends ILazyOperator
@@ -70,7 +90,7 @@ public abstract class Fluff
         protected String name;
         int numParams;
 
-        AbstractLazyFunction(int numParams, String name)
+        public AbstractLazyFunction(int numParams, String name)
         {
             this.numParams = numParams;
             this.name = name;
@@ -89,7 +109,7 @@ public abstract class Fluff
             return numParams < 0;
         }
 
-        public static List<Value> unpackLazy(List<LazyValue> lzargs, Context c, int contextType)
+        public static List<Value> unpackLazy(List<LazyValue> lzargs, Context c, Context.Type contextType)
         {
             List<Value> args = new ArrayList<>();
             for (LazyValue lv : lzargs)
@@ -103,7 +123,7 @@ public abstract class Fluff
             return args;
         }
 
-        public List<Value> unpackArgs(List<LazyValue> lzargs, Context c, int contextType)
+        public List<Value> unpackArgs(List<LazyValue> lzargs, Context c, Context.Type contextType)
         {
             List<Value> args = new ArrayList<>();
             for (LazyValue lv : lzargs)
@@ -118,6 +138,13 @@ public abstract class Fluff
                 throw new InternalExpressionException("Function " + getName() + " expected " + getNumParams() + " parameters, got " + args.size());
             return args;
         }
+
+        public static List<LazyValue> lazify(List<Value> args)
+        {
+            List<LazyValue> lzargs = new ArrayList<>(args.size());
+            args.forEach( v -> lzargs.add( (c, t) -> v));
+            return lzargs;
+        }
     }
 
     public abstract static class AbstractFunction extends AbstractLazyFunction implements IFunction
@@ -127,7 +154,17 @@ public abstract class Fluff
         }
 
         @Override
-        public LazyValue lazyEval(Context cc, Integer type, Expression e, Tokenizer.Token t, final List<LazyValue> lazyParams)
+        public boolean pure() {
+            return true;
+        }
+
+        @Override
+        public boolean transitive() {
+            return false;
+        }
+
+        @Override
+        public LazyValue lazyEval(Context cc, Context.Type type, Expression e, Tokenizer.Token t, final List<LazyValue> lazyParams)
         {
             try
             {
@@ -135,7 +172,7 @@ public abstract class Fluff
                 { // eager evaluation always ignores the required type and evals params by none default
                     private List<Value> params;
 
-                    public Value evalValue(Context c, Integer type) {
+                    public Value evalValue(Context c, Context.Type type) {
                         ILazyFunction.checkInterrupts();
                         return AbstractFunction.this.eval(getParams(c));
                     }
@@ -143,7 +180,7 @@ public abstract class Fluff
                     private List<Value> getParams(Context c) {
                         if (params == null) {
                             // very likely needs to be dynamic, so not static like here, or remember if it was.
-                            params = unpackArgs(lazyParams, c, Context.NONE);
+                            params = unpackArgs(lazyParams, c, Context.Type.NONE);
                         }
                         else
                         {
@@ -187,13 +224,22 @@ public abstract class Fluff
         AbstractOperator(int precedence, boolean leftAssoc) {
             super(precedence, leftAssoc);
         }
+        @Override
+        public boolean pure() {
+            return true;
+        }
 
         @Override
-        public LazyValue lazyEval(Context cc, Integer type, Expression e, Tokenizer.Token t, final LazyValue v1, final LazyValue v2)
+        public boolean transitive() {
+            return false;
+        }
+
+        @Override
+        public LazyValue lazyEval(Context cc, Context.Type type, Expression e, Tokenizer.Token t, final LazyValue v1, final LazyValue v2)
         {
             try
             {
-                return (c, type_ignored) -> AbstractOperator.this.eval(v1.evalValue(c, Context.NONE), v2.evalValue(c, Context.NONE));
+                return (c, type_ignored) -> AbstractOperator.this.eval(v1.evalValue(c, Context.Type.NONE), v2.evalValue(c, Context.Type.NONE));
             }
             catch (RuntimeException exc)
             {
@@ -207,9 +253,18 @@ public abstract class Fluff
         AbstractUnaryOperator(int precedence, boolean leftAssoc) {
             super(precedence, leftAssoc);
         }
+        @Override
+        public boolean pure() {
+            return true;
+        }
 
         @Override
-        public LazyValue lazyEval(Context cc, Integer type, Expression e, Tokenizer.Token t, final LazyValue v1, final LazyValue v2)
+        public boolean transitive() {
+            return false;
+        }
+
+        @Override
+        public LazyValue lazyEval(Context cc, Context.Type type, Expression e, Tokenizer.Token t, final LazyValue v1, final LazyValue v2)
         {
             try
             {
@@ -217,7 +272,7 @@ public abstract class Fluff
                 {
                     throw new ExpressionException(cc, e, t, "Did not expect a second parameter for unary operator");
                 }
-                return (c, ignored_type) -> AbstractUnaryOperator.this.evalUnary(v1.evalValue(c, Context.NONE));
+                return (c, ignored_type) -> AbstractUnaryOperator.this.evalUnary(v1.evalValue(c, Context.Type.NONE));
             }
             catch (RuntimeException exc)
             {

src/main/java/carpet/script/LazyValue.java

@@ -10,15 +10,50 @@ public interface LazyValue
     LazyValue TRUE = (c, t) -> Value.TRUE;
     LazyValue NULL = (c, t) -> Value.NULL;
     LazyValue ZERO = (c, t) -> Value.ZERO;
-    /**
-     * The Value representation of the left parenthesis, used for parsing
-     * varying numbers of function parameters.
-     */
-    LazyValue PARAMS_START = (c, t) -> null;
 
-    Value evalValue(Context c, Integer type);
+    public static LazyValue ofConstant(Value val) {
+        return new Constant(val);
+    }
+
+    Value evalValue(Context c, Context.Type type);
 
     default Value evalValue(Context c){
-        return evalValue(c, Context.NONE);
+        return evalValue(c, Context.Type.NONE);
+    }
+
+    @FunctionalInterface
+    interface ContextFreeLazyValue extends LazyValue
+    {
+
+        Value evalType(Context.Type type);
+
+        @Override
+        default Value evalValue(Context c, Context.Type type) {
+            return evalType(type);
+        }
+    }
+
+
+    class Constant implements ContextFreeLazyValue
+    {
+        Value result;
+
+        public Constant(Value value)
+        {
+            result = value;
+        }
+
+        public Value get() {return result;}
+
+        @Override
+        public Value evalType(Context.Type type) {
+
+            return result.fromConstant();
+        }
+
+        @Override
+        public Value evalValue(Context c, Context.Type type) {
+            return result.fromConstant();
+        }
     }
 }

src/main/java/carpet/script/ScriptHost.java

@@ -2,6 +2,7 @@ package carpet.script;
 
 import carpet.script.bundled.Module;
 import carpet.script.exception.ExpressionException;
+import carpet.script.exception.IntegrityException;
 import carpet.script.exception.InternalExpressionException;
 import carpet.script.language.Arithmetic;
 import carpet.script.value.FunctionValue;
@@ -121,11 +122,6 @@ public abstract class ScriptHost
 
     void initializeModuleGlobals(ModuleData md)
     {
-        md.globalVariables.put("euler", (c, t) -> Arithmetic.euler);
-        md.globalVariables.put("pi", (c, t) -> Arithmetic.PI);
-        md.globalVariables.put("null", (c, t) -> Value.NULL);
-        md.globalVariables.put("true", (c, t) -> Value.TRUE);
-        md.globalVariables.put("false", (c, t) -> Value.FALSE);
     }
 
     public void importModule(Context c, String moduleName)
@@ -181,8 +177,8 @@ public abstract class ScriptHost
             throw new InternalExpressionException("Cannot import from module that is not imported");
         }
         return Stream.concat(
-                globaVariableNames(source, s -> s.startsWith("global_")),
-                globaFunctionNames(source, s -> true)
+                globalVariableNames(source, s -> s.startsWith("global_")),
+                globalFunctionNames(source, s -> true)
         ).distinct().sorted();
     }
 
@@ -205,7 +201,7 @@ public abstract class ScriptHost
     }
     private FunctionValue getFunction(Module module, String name)
     {
-        ModuleData local = moduleData.get(module);
+        ModuleData local = getModuleData(module);
         FunctionValue ret = local.globalFunctions.get(name); // most uses would be from local scope anyways
         if (ret != null) return ret;
         ModuleData target = local.functionImports.get(name);
@@ -239,7 +235,7 @@ public abstract class ScriptHost
     public LazyValue getGlobalVariable(String name) { return getGlobalVariable(main, name); }
     public LazyValue getGlobalVariable(Module module, String name)
     {
-        ModuleData local = moduleData.get(module);
+        ModuleData local = getModuleData(module);
         LazyValue ret = local.globalVariables.get(name); // most uses would be from local scope anyways
         if (ret != null) return ret;
         ModuleData target = local.globalsImports.get(name);
@@ -272,55 +268,62 @@ public abstract class ScriptHost
 
     public void delFunctionWithPrefix(Module module, String prefix)
     {
-        ModuleData data = moduleData.get(module);
+        ModuleData data = getModuleData(module);
         data.globalFunctions.entrySet().removeIf(e -> e.getKey().startsWith(prefix));
         data.functionImports.entrySet().removeIf(e -> e.getKey().startsWith(prefix));
     }
     public void delFunction(Module module, String funName)
     {
-        ModuleData data = moduleData.get(module);
+        ModuleData data = getModuleData(module);
         data.globalFunctions.remove(funName);
         data.functionImports.remove(funName);
     }
 
     public void delGlobalVariableWithPrefix(Module module, String prefix)
     {
-        ModuleData data = moduleData.get(module);
+        ModuleData data = getModuleData(module);
         data.globalVariables.entrySet().removeIf(e -> e.getKey().startsWith(prefix));
         data.globalsImports.entrySet().removeIf(e -> e.getKey().startsWith(prefix));
     }
 
     public void delGlobalVariable(Module module, String varName)
     {
-        ModuleData data = moduleData.get(module);
+        ModuleData data = getModuleData(module);
         data.globalFunctions.remove(varName);
         data.functionImports.remove(varName);
     }
 
+    private ModuleData getModuleData(Module module)
+    {
+        ModuleData data = moduleData.get(module);
+        if (data == null) throw new IntegrityException("Module structure changed for the app. Did you reload the app with tasks running?");
+        return data;
+    }
+
     public void addUserDefinedFunction(Context ctx, Module module, String name, FunctionValue fun)
     {
-        moduleData.get(module).globalFunctions.put(name, fun);
+        getModuleData(module).globalFunctions.put(name, fun);
     }
 
     public void setGlobalVariable(Module module, String name, LazyValue lv)
     {
-        moduleData.get(module).globalVariables.put(name, lv);
+        getModuleData(module).globalVariables.put(name, lv);
     }
 
-    public Stream<String> globaVariableNames(Module module, Predicate<String> predicate)
+    public Stream<String> globalVariableNames(Module module, Predicate<String> predicate)
     {
         return Stream.concat(Stream.concat(
-                moduleData.get(module).globalVariables.keySet().stream(),
-                moduleData.get(module).globalsImports.keySet().stream()
-        ), moduleData.get(module).futureImports.keySet().stream().filter(s -> s.startsWith("global_"))).filter(predicate);
+                getModuleData(module).globalVariables.keySet().stream(),
+                getModuleData(module).globalsImports.keySet().stream()
+        ), getModuleData(module).futureImports.keySet().stream().filter(s -> s.startsWith("global_"))).filter(predicate);
     }
 
-    public Stream<String> globaFunctionNames(Module module, Predicate<String> predicate)
+    public Stream<String> globalFunctionNames(Module module, Predicate<String> predicate)
     {
         return Stream.concat(Stream.concat(
-                moduleData.get(module).globalFunctions.keySet().stream(),
-                moduleData.get(module).functionImports.keySet().stream()
-        ),moduleData.get(module).futureImports.keySet().stream().filter(s -> !s.startsWith("global_"))).filter(predicate);
+                getModuleData(module).globalFunctions.keySet().stream(),
+                getModuleData(module).functionImports.keySet().stream()
+        ),getModuleData(module).futureImports.keySet().stream().filter(s -> !s.startsWith("global_"))).filter(predicate);
     }
 
     public ScriptHost retrieveForExecution(String /*Nullable*/ user)

src/main/java/carpet/script/Tokenizer.java

@@ -398,8 +398,28 @@ public class Tokenizer implements Iterator<Tokenizer.Token>
     {
         enum TokenType
         {
-            VARIABLE, FUNCTION, LITERAL, OPERATOR, UNARY_OPERATOR,
-            OPEN_PAREN, COMMA, CLOSE_PAREN, HEX_LITERAL, STRINGPARAM, MARKER
+            FUNCTION(true, false), OPERATOR(true, false), UNARY_OPERATOR(true, false),
+            VARIABLE(false, false), CONSTANT(false, true),
+            LITERAL(false, true), HEX_LITERAL(false, true), STRINGPARAM(false, true),
+            OPEN_PAREN(false, true), COMMA(false, true), CLOSE_PAREN(false, true), MARKER(false, true);
+
+            boolean functional;
+            boolean constant;
+
+            TokenType(boolean functional, boolean constant)
+            {
+                this.functional = functional;
+                this.constant = constant;
+            }
+
+            public boolean isFunctional()
+            {
+                return functional;
+            }
+
+            public boolean isConstant() {
+                return constant;
+            }
         }
         public String surface = "";
         public TokenType type;

src/main/java/carpet/script/api/Auxiliary.java

@@ -796,7 +796,7 @@ public class Auxiliary {
             return Value.TRUE;
         });
 
-        expression.addFunction("logger", lv ->
+        expression.addImpureFunction("logger", lv ->
         {
             Value res;
 

src/main/java/carpet/script/api/Threading.java

@@ -25,7 +25,7 @@ public class Threading
         });
 
         // has to be lazy due to deferred execution of the expression
-        expression.addLazyFunctionWithDelegation("task_dock", 1, (c, t, expr, tok, lv) -> {
+        expression.addLazyFunctionWithDelegation("task_dock", 1, false,true, (c, t, expr, tok, lv) -> {
             CarpetContext cc = (CarpetContext)c;
             MinecraftServer server = cc.s.getMinecraftServer();
             if (server.isOnThread()) return lv.get(0); // pass through for on thread tasks

src/main/java/carpet/script/exception/IntegrityException.java

@@ -0,0 +1,9 @@
+package carpet.script.exception;
+
+public class IntegrityException extends RuntimeException
+{
+    public IntegrityException(String message)
+    {
+        super(message);
+    }
+}

src/main/java/carpet/script/language/Arithmetic.java

@@ -3,6 +3,7 @@ package carpet.script.language;
 import carpet.script.Context;
 import carpet.script.Expression;
 import carpet.script.exception.InternalExpressionException;
+import carpet.script.value.BooleanValue;
 import carpet.script.value.ListValue;
 import carpet.script.value.NumericValue;
 import carpet.script.value.Value;
@@ -15,7 +16,7 @@ public class Arithmetic {
 
     public static void apply(Expression expression)
     {
-        expression.addLazyFunction("not", 1, (c, t, lv) -> lv.get(0).evalValue(c, Context.BOOLEAN).getBoolean() ? ((cc, tt) -> Value.FALSE) : ((cc, tt) -> Value.TRUE));
+        expression.addTypedContextFunction("not", 1, Context.Type.BOOLEAN, (c, t, lv) -> BooleanValue.of(lv.get(0).getBoolean()) );
         expression.addUnaryFunction("fact", (v) ->
         {
             long number = NumericValue.asNumber(v).getLong();

src/main/java/carpet/script/language/ControlFlow.java

@@ -21,13 +21,22 @@ public class ControlFlow {
     public static void apply(Expression expression) // public just to get the javadoc right
     {
         // needs to be lazy cause of custom contextualization
-        expression.addLazyBinaryOperator(";", Operators.precedence.get("nextop;"), true, (c, t, lv1, lv2) ->
+        expression.addLazyBinaryOperator(";", Operators.precedence.get("nextop;"), true, true, t -> Context.Type.VOID, (c, t, lv1, lv2) ->
         {
             lv1.evalValue(c, Context.VOID);
             Value v2 = lv2.evalValue(c, t);
             return (cc, tt) -> v2;
         });
 
+        expression.addPureLazyFunction("then", -1, t -> Context.Type.VOID, (c, t, lv) -> {
+            int imax = lv.size()-1;
+            for (int i = 0; i < imax; i++) lv.get(i).evalValue(c, Context.VOID);
+            Value v = lv.get(imax).evalValue(c, t);
+            return (cc, tt) -> v;
+        });
+        expression.addFunctionalEquivalence(";", "then");
+
+
         // obvious lazy due to conditional evaluation of arguments
         expression.addLazyFunction("if", -1, (c, t, lv) ->
         {
@@ -50,9 +59,9 @@ public class ControlFlow {
             return (cc, tt) -> Value.NULL;
         });
 
-        expression.addFunction("exit", (lv) -> { throw new ExitStatement(lv.size()==0?Value.NULL:lv.get(0)); });
+        expression.addImpureFunction("exit", (lv) -> { throw new ExitStatement(lv.size()==0?Value.NULL:lv.get(0)); });
 
-        expression.addFunction("throw", lv->
+        expression.addImpureFunction("throw", lv->
         {
             switch (lv.size()) 
             {

src/main/java/carpet/script/language/DataStructures.java

@@ -189,7 +189,7 @@ public class DataStructures {
             return Value.NULL;
         });
 
-        expression.addBinaryContextOperator(":", Operators.precedence.get("attribute~:"),true, (c, t, container, address) ->
+        expression.addBinaryContextOperator(":", Operators.precedence.get("attribute~:"),true, true, false, (ctx, t, container, address) ->
         {
             if (container instanceof LContainerValue)
             {

src/main/java/carpet/script/language/Functions.java

@@ -3,6 +3,8 @@ package carpet.script.language;
 import carpet.script.Context;
 import carpet.script.Expression;
 import carpet.script.Fluff;
+import carpet.script.LazyValue;
+import carpet.script.Tokenizer;
 import carpet.script.argument.FunctionArgument;
 import carpet.script.exception.InternalExpressionException;
 import carpet.script.exception.ReturnStatement;
@@ -35,53 +37,75 @@ public class Functions {
             return ListValue.wrap(c.host.availableImports(moduleName).map(StringValue::new).collect(Collectors.toList()));
         });
 
+
         // needs to be lazy because of custom context of execution of arguments as a signature
-        expression.addLazyFunctionWithDelegation("call",-1, (c, t, expr, tok, lv) ->
-        { // adjust based on c
-            if (lv.size() == 0)
-                throw new InternalExpressionException("'call' expects at least function name to call");
-            //lv.remove(lv.size()-1); // aint gonna cut it // maybe it will because of the eager eval changes
-            if (t != Context.SIGNATURE) // just call the function
+        expression.addCustomFunction("call", new Fluff.AbstractLazyFunction(-1, "call") {
+            @Override
+            public LazyValue lazyEval(Context c, Context.Type t, Expression expr, Tokenizer.Token tok, List<LazyValue> lv)
             {
-                List<Value> args = Fluff.AbstractFunction.unpackLazy(lv, c, Context.NONE);
-                FunctionArgument functionArgument = FunctionArgument.findIn(c, expression.module, args, 0, false, true);
-                FunctionValue fun = functionArgument.function;
-                return fun.callInContext(c, t, functionArgument.args);
-            }
-            // gimme signature
-            String name = lv.get(0).evalValue(c, Context.NONE).getString();
-            List<String> args = new ArrayList<>();
-            List<String> globals = new ArrayList<>();
-            String varArgs = null;
-            for (int i = 1; i < lv.size(); i++)
-            {
-                Value v = lv.get(i).evalValue(c, Context.LOCALIZATION);
-                if (!v.isBound())
+                if (lv.size() == 0)
+                    throw new InternalExpressionException("'call' expects at least function name to call");
+                //lv.remove(lv.size()-1); // aint gonna cut it // maybe it will because of the eager eval changes
+                if (t != Context.SIGNATURE) // just call the function
                 {
-                    throw new InternalExpressionException("Only variables can be used in function signature, not  " + v.getString());
+                    List<Value> args = Fluff.AbstractFunction.unpackLazy(lv, c, Context.NONE);
+                    FunctionArgument functionArgument = FunctionArgument.findIn(c, expression.module, args, 0, false, true);
+                    FunctionValue fun = functionArgument.function;
+                    return fun.callInContext(c, t, functionArgument.args);
                 }
-                if (v instanceof FunctionAnnotationValue)
+                // gimme signature
+                String name = lv.get(0).evalValue(c, Context.NONE).getString();
+                List<String> args = new ArrayList<>();
+                List<String> globals = new ArrayList<>();
+                String varArgs = null;
+                for (int i = 1; i < lv.size(); i++)
                 {
-                    if (((FunctionAnnotationValue) v).type == FunctionAnnotationValue.Type.GLOBAL)
+                    Value v = lv.get(i).evalValue(c, Context.LOCALIZATION);
+                    if (!v.isBound())
                     {
-                        globals.add(v.boundVariable);
+                        throw new InternalExpressionException("Only variables can be used in function signature, not  " + v.getString());
+                    }
+                    if (v instanceof FunctionAnnotationValue)
+                    {
+                        if (((FunctionAnnotationValue) v).type == FunctionAnnotationValue.Type.GLOBAL)
+                        {
+                            globals.add(v.boundVariable);
+                        }
+                        else
+                        {
+                            if (varArgs != null)
+                                throw new InternalExpressionException("Variable argument identifier is already defined as "+varArgs+", trying to overwrite with "+v.boundVariable);
+                            varArgs = v.boundVariable;
+                        }
                     }
                     else
                     {
-                        if (varArgs != null)
-                            throw new InternalExpressionException("Variable argument identifier is already defined as "+varArgs+", trying to overwrite with "+v.boundVariable);
-                        varArgs = v.boundVariable;
+                        args.add(v.boundVariable);
                     }
                 }
-                else
-                {
-                    args.add(v.boundVariable);
-                }
+                Value retval = new FunctionSignatureValue(name, args, varArgs, globals);
+                return (cc, tt) -> retval;
+            }
+
+            @Override
+            public boolean pure()
+            {
+                return false; //true for sinature, but lets leave it for later
+            }
+
+            @Override
+            public boolean transitive() {
+                return false;
+            }
+
+            @Override
+            public Context.Type staticType(Context.Type outerType)
+            {
+                return outerType==Context.SIGNATURE?Context.LOCALIZATION:Context.NONE;
             }
-            Value retval = new FunctionSignatureValue(name, args, varArgs, globals);
-            return (cc, tt) -> retval;
         });
 
+
         expression.addContextFunction("outer", 1, (c, t, lv) ->
         {
             if (t != Context.LOCALIZATION)
@@ -91,7 +115,7 @@ public class Functions {
 
         //assigns const procedure to the lhs, returning its previous value
         // must be lazy due to RHS being an expression to save to execute
-        expression.addLazyBinaryOperatorWithDelegation("->", Operators.precedence.get("def->"), false, (c, type, e, t, lv1, lv2) ->
+        expression.addLazyBinaryOperatorWithDelegation("->", Operators.precedence.get("def->"), false, false, (c, type, e, t, lv1, lv2) ->
         {
             if (type == Context.MAPDEF)
             {
@@ -106,6 +130,6 @@ public class Functions {
             return (cc, tt) -> result;
         });
 
-        expression.addFunction("return", (lv) -> { throw new ReturnStatement(lv.size()==0?Value.NULL:lv.get(0));} );
+        expression.addImpureFunction("return", (lv) -> { throw new ReturnStatement(lv.size()==0?Value.NULL:lv.get(0));} );
     }
 }

src/main/java/carpet/script/language/Loops.java

@@ -21,14 +21,14 @@ public class Loops {
         // condition and expression will get a bound '_i'
         // returns last successful expression or false
         // while(cond, limit, expr) => ??
-        expression.addFunction("break", lv ->
+        expression.addImpureFunction("break", lv ->
         {
             if (lv.size()==0) throw new BreakStatement(null);
             if (lv.size()==1) throw new BreakStatement(lv.get(0));
             throw new InternalExpressionException("'break' can only be called with zero or one argument");
         });
 
-        expression.addFunction("continue", lv ->
+        expression.addImpureFunction("continue", lv ->
         {
             if (lv.size()==0) throw new ContinueStatement(null);
             if (lv.size()==1) throw new ContinueStatement(lv.get(0));

src/main/java/carpet/script/language/Operators.java

@@ -5,6 +5,7 @@ import carpet.script.Expression;
 import carpet.script.LazyValue;
 import carpet.script.exception.InternalExpressionException;
 import carpet.script.value.AbstractListValue;
+import carpet.script.value.BooleanValue;
 import carpet.script.value.ContainerValueInterface;
 import carpet.script.value.FunctionAnnotationValue;
 import carpet.script.value.FunctionUnpackedArgumentsValue;
@@ -14,6 +15,7 @@ import carpet.script.value.MapValue;
 import carpet.script.value.NumericValue;
 import carpet.script.value.Value;
 
+import java.util.Comparator;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
@@ -38,47 +40,203 @@ public class Operators {
     public static void apply(Expression expression)
     {
         expression.addBinaryOperator("+", precedence.get("addition+-"), true, Value::add);
+        expression.addFunction("sum", lv -> {
+            int size = lv.size();
+            if (size == 0) return Value.NULL;
+            Value accumulator = lv.get(0);
+            for (Value v: lv.subList(1, size)) accumulator = accumulator.add(v);
+            return accumulator;
+        });
+        expression.addFunctionalEquivalence("+", "sum");
+
         expression.addBinaryOperator("-", precedence.get("addition+-"), true, Value::subtract);
+        expression.addFunction("difference", lv -> {
+            int size = lv.size();
+            if (size == 0) return Value.NULL;
+            Value accumulator = lv.get(0);
+            for (Value v: lv.subList(1, size)) accumulator = accumulator.subtract(v);
+            return accumulator;
+        });
+        expression.addFunctionalEquivalence("-", "difference");
+
         expression.addBinaryOperator("*", precedence.get("multiplication*/%"), true, Value::multiply);
+        expression.addFunction("product", lv -> {
+            int size = lv.size();
+            if (size == 0) return Value.NULL;
+            Value accumulator = lv.get(0);
+            for (Value v: lv.subList(1, size)) accumulator = accumulator.multiply(v);
+            return accumulator;
+        });
+        expression.addFunctionalEquivalence("*", "product");
+
         expression.addBinaryOperator("/", precedence.get("multiplication*/%"), true, Value::divide);
+        expression.addFunction("quotient", lv -> {
+            int size = lv.size();
+            if (size == 0) return Value.NULL;
+            Value accumulator = lv.get(0);
+            for (Value v: lv.subList(1, size)) accumulator = accumulator.multiply(v);
+            return accumulator;
+        });
+        expression.addFunctionalEquivalence("/", "quotient");
+
         expression.addBinaryOperator("%", precedence.get("multiplication*/%"), true, (v1, v2) ->
                 new NumericValue(NumericValue.asNumber(v1).getDouble() % NumericValue.asNumber(v2).getDouble()));
         expression.addBinaryOperator("^", precedence.get("exponent^"), false, (v1, v2) ->
                 new NumericValue(java.lang.Math.pow(NumericValue.asNumber(v1).getDouble(), NumericValue.asNumber(v2).getDouble())));
 
         // lazy cause RHS is only conditional
-        expression.addLazyBinaryOperator("&&", precedence.get("and&&"), false, (c, t, lv1, lv2) ->
-        {
+        expression.addLazyBinaryOperator("&&", precedence.get("and&&"), false, true, t -> Context.Type.BOOLEAN, (c, t, lv1, lv2) ->
+        { // todo check how is optimizations going
             Value v1 = lv1.evalValue(c, Context.BOOLEAN);
             if (!v1.getBoolean()) return (cc, tt) -> v1;
             return lv2;
         });
 
+        expression.addPureLazyFunction("and", -1, t -> Context.Type.BOOLEAN, (c, t, lv) -> {
+            int last = lv.size()-1;
+            if (last == -1) return LazyValue.TRUE;
+            for (LazyValue l: lv.subList(0, last))
+            {
+                Value val = l.evalValue(c, Context.Type.BOOLEAN);
+                if (val instanceof FunctionUnpackedArgumentsValue)
+                {
+                    for (Value it : (FunctionUnpackedArgumentsValue) val)
+                        if (!it.getBoolean()) return (cc, tt) -> it;
+                }
+                else
+                {
+                    if (!val.getBoolean()) return (cc, tt) -> val;
+                }
+            }
+            return lv.get(last);
+        });
+        expression.addFunctionalEquivalence("&&", "and");
+
         // lazy cause RHS is only conditional
-        expression.addLazyBinaryOperator("||", precedence.get("or||"), false, (c, t, lv1, lv2) ->
+        expression.addLazyBinaryOperator("||", precedence.get("or||"), false, true, t -> Context.Type.BOOLEAN, (c, t, lv1, lv2) ->
         {
             Value v1 = lv1.evalValue(c, Context.BOOLEAN);
             if (v1.getBoolean()) return (cc, tt) -> v1;
             return lv2;
         });
 
+        expression.addPureLazyFunction("or", -1, t -> Context.Type.BOOLEAN, (c, t, lv) -> {
+            int last = lv.size()-1;
+            if (last == -1) return LazyValue.FALSE;
+            for (LazyValue l: lv.subList(0, last))
+            {
+                Value val = l.evalValue(c, Context.Type.BOOLEAN);
+                if (val instanceof FunctionUnpackedArgumentsValue)
+                {
+                    for (Value it : (FunctionUnpackedArgumentsValue) val)
+                        if (it.getBoolean()) return (cc, tt) -> it;
+                }
+                else
+                {
+                    if (val.getBoolean()) return (cc, tt) -> val;
+                }
+            }
+            return lv.get(last);
+        });
+        expression.addFunctionalEquivalence("||", "or");
+
         expression.addBinaryOperator("~", precedence.get("attribute~:"), true, Value::in);
 
         expression.addBinaryOperator(">", precedence.get("compare>=><=<"), false, (v1, v2) ->
-                v1.compareTo(v2) > 0 ? Value.TRUE : Value.FALSE);
+                BooleanValue.of(v1.compareTo(v2) > 0));
+        expression.addFunction("decreasing", lv -> {
+            int size = lv.size();
+            if (size < 2) return Value.TRUE;
+            Value prev = lv.get(0);
+            for (Value next: lv.subList(1, size))
+            {
+                if (prev.compareTo(next) <= 0) return Value.FALSE;
+                prev = next;
+            }
+            return Value.TRUE;
+        });
+        expression.addFunctionalEquivalence(">", "decreasing");
+
         expression.addBinaryOperator(">=", precedence.get("compare>=><=<"), false, (v1, v2) ->
-                v1.compareTo(v2) >= 0 ? Value.TRUE : Value.FALSE);
+                BooleanValue.of(v1.compareTo(v2) >= 0));
+        expression.addFunction("nonincreasing", lv -> {
+            int size = lv.size();
+            if (size < 2) return Value.TRUE;
+            Value prev = lv.get(0);
+            for (Value next: lv.subList(1, size))
+            {
+                if (prev.compareTo(next) < 0) return Value.FALSE;
+                prev = next;
+            }
+            return Value.TRUE;
+        });
+        expression.addFunctionalEquivalence(">=", "nonincreasing");
+
         expression.addBinaryOperator("<", precedence.get("compare>=><=<"), false, (v1, v2) ->
-                v1.compareTo(v2) < 0 ? Value.TRUE : Value.FALSE);
+                BooleanValue.of(v1.compareTo(v2) < 0));
+        expression.addFunction("increasing", lv -> {
+            int size = lv.size();
+            if (size < 2) return Value.TRUE;
+            Value prev = lv.get(0);
+            for (Value next: lv.subList(1, size))
+            {
+                if (prev.compareTo(next) >= 0) return Value.FALSE;
+                prev = next;
+            }
+            return Value.TRUE;
+        });
+        expression.addFunctionalEquivalence("<", "increasing");
+
         expression.addBinaryOperator("<=", precedence.get("compare>=><=<"), false, (v1, v2) ->
-                v1.compareTo(v2) <= 0 ? Value.TRUE : Value.FALSE);
+                BooleanValue.of(v1.compareTo(v2) <= 0));
+        expression.addFunction("nondecreasing", lv -> {
+            int size = lv.size();
+            if (size < 2) return Value.TRUE;
+            Value prev = lv.get(0);
+            for (Value next: lv.subList(1, size))
+            {
+                if (prev.compareTo(next) > 0) return Value.FALSE;
+                prev = next;
+            }
+            return Value.TRUE;
+        });
+        expression.addFunctionalEquivalence("<=", "nondecreasing");
+
         expression.addBinaryOperator("==", precedence.get("equal==!="), false, (v1, v2) ->
                 v1.equals(v2) ? Value.TRUE : Value.FALSE);
+        expression.addFunction("equal", lv -> {
+            int size = lv.size();
+            if (size < 2) return Value.TRUE;
+            Value prev = lv.get(0);
+            for (Value next: lv.subList(1, size))
+            {
+                if (!prev.equals(next)) return Value.FALSE;
+                prev = next;
+            }
+            return Value.TRUE;
+        });
+        expression.addFunctionalEquivalence("==", "equal");
+
+
         expression.addBinaryOperator("!=", precedence.get("equal==!="), false, (v1, v2) ->
                 v1.equals(v2) ? Value.FALSE : Value.TRUE);
+        expression.addFunction("unique", lv -> {
+            int size = lv.size();
+            if (size < 2) return Value.TRUE;
+            // need to order them so same obejects will be next to each other.
+            lv.sort(Comparator.comparingInt(Value::hashCode));
+            Value prev = lv.get(0);
+            for (Value next: lv.subList(1, size))
+            {
+                if (prev.equals(next)) return Value.FALSE;
+                prev = next;
+            }
+            return Value.TRUE;
+        });
+        expression.addFunctionalEquivalence("!=", "unique");
 
         // lazy cause of assignment which is non-trivial
-        expression.addLazyBinaryOperator("=", precedence.get("assign=<>"), false, (c, t, lv1, lv2) ->
+        expression.addLazyBinaryOperator("=", precedence.get("assign=<>"), false, false, t -> Context.Type.LVALUE, (c, t, lv1, lv2) ->
         {
             Value v1 = lv1.evalValue(c, Context.LVALUE);
             Value v2 = lv2.evalValue(c);
@@ -117,7 +275,7 @@ public class Operators {
         });
 
         // lazy due to assignment
-        expression.addLazyBinaryOperator("+=", precedence.get("assign=<>"), false, (c, t, lv1, lv2) ->
+        expression.addLazyBinaryOperator("+=", precedence.get("assign=<>"), false, false, t -> Context.Type.LVALUE, (c, t, lv1, lv2) ->
         {
             Value v1 = lv1.evalValue(c, Context.LVALUE);
             Value v2 = lv2.evalValue(c);
@@ -177,7 +335,7 @@ public class Operators {
             return boundedLHS;
         });
 
-        expression.addBinaryContextOperator("<>", precedence.get("assign=<>"), false, (c, t, v1, v2) ->
+        expression.addBinaryContextOperator("<>", precedence.get("assign=<>"), false, false, false, (c, t, v1, v2) ->
         {
             if (v1 instanceof ListValue.ListConstructorValue && v2 instanceof ListValue.ListConstructorValue)
             {
@@ -218,12 +376,12 @@ public class Operators {
         expression.addUnaryOperator("+", false, NumericValue::asNumber);
 
         // could be non-lazy, but who cares - its a small one.
-        expression.addLazyUnaryOperator("!", precedence.get("unary+-!..."), false, (c, t, lv) ->
+        expression.addLazyUnaryOperator("!", precedence.get("unary+-!..."), false, true, x -> Context.Type.BOOLEAN, (c, t, lv) ->
                 lv.evalValue(c, Context.BOOLEAN).getBoolean() ? (cc, tt)-> Value.FALSE : (cc, tt) -> Value.TRUE
         ); // might need context boolean
 
         // lazy because of typed evaluation of the argument
-        expression.addLazyUnaryOperator("...", Operators.precedence.get("unary+-!..."), false, (c, t, lv) ->
+        expression.addLazyUnaryOperator("...", Operators.precedence.get("unary+-!..."), false, true, t -> t== Context.Type.LOCALIZATION?Context.NONE:t, (c, t, lv) ->
         {
             if (t == Context.LOCALIZATION)
                 return (cc, tt) -> new FunctionAnnotationValue(lv.evalValue(c), FunctionAnnotationValue.Type.VARARG);

src/main/java/carpet/script/language/Sys.java

@@ -36,7 +36,7 @@ public class Sys {
     {
         expression.addUnaryFunction("hash_code", v -> new NumericValue(v.hashCode()));
 
-        expression.addUnaryFunction("copy", Value::deepcopy);
+        expression.addImpureUnaryFunction("copy", Value::deepcopy);
 
         expression.addTypedContextFunction("bool", 1, Context.BOOLEAN, (c, t, lv) ->
         {
@@ -414,7 +414,7 @@ public class Sys {
             List<Value> values = new ArrayList<>();
             if (prefix.startsWith("global"))
             {
-                c.host.globaVariableNames(expression.module, (s) -> s.startsWith(prefix)).forEach(s -> values.add(new StringValue(s)));
+                c.host.globalVariableNames(expression.module, (s) -> s.startsWith(prefix)).forEach(s -> values.add(new StringValue(s)));
             }
             else
             {

src/main/java/carpet/script/language/Threading.java

@@ -12,7 +12,7 @@ public class Threading
 {
     public static void apply(Expression expression)
     {
-        expression.addFunctionWithDelegation("task", -1, (c, t, expr, tok, lv) ->
+        expression.addFunctionWithDelegation("task", -1, false, false, (c, t, expr, tok, lv) ->
         {
             if (lv.size() == 0)
                 throw new InternalExpressionException("'task' requires at least function to call as a parameter");
@@ -22,7 +22,7 @@ public class Threading
             return thread;
         });
 
-        expression.addFunctionWithDelegation("task_thread", -1, (c, t, expr, tok, lv) ->
+        expression.addFunctionWithDelegation("task_thread", -1, false, false, (c, t, expr, tok, lv) ->
         {
             if (lv.size() < 2)
                 throw new InternalExpressionException("'task' requires at least function to call as a parameter");

src/main/java/carpet/script/value/AbstractListValue.java

@@ -15,4 +15,9 @@ public abstract class AbstractListValue extends Value implements Iterable<Value>
     {
         throw new InternalExpressionException("Cannot append a value to an abstract list");
     }
+
+    @Override
+    public Value fromConstant() {
+        return this.deepcopy();
+    }
 }

src/main/java/carpet/script/value/FunctionValue.java

@@ -150,7 +150,7 @@ public class FunctionValue extends Value implements Fluff.ILazyFunction
         return varArgs != null;
     }
 
-    public LazyValue callInContext(Context c, Integer type, List<Value> params)
+    public LazyValue callInContext(Context c, Context.Type type, List<Value> params)
     {
         try
         {
@@ -204,12 +204,12 @@ public class FunctionValue extends Value implements Fluff.ILazyFunction
     }
 
     @Override
-    public LazyValue lazyEval(Context c, Integer type, Expression e, Tokenizer.Token t, List<LazyValue> lazyParams) {
+    public LazyValue lazyEval(Context c, Context.Type type, Expression e, Tokenizer.Token t, List<LazyValue> lazyParams) {
         List<Value> resolvedParams = unpackArgs(lazyParams, c);
         return execute(c, type, e, t, resolvedParams);
     }
 
-    public LazyValue execute(Context c, Integer type, Expression e, Tokenizer.Token t, List<Value> params)
+    public LazyValue execute(Context c, Context.Type type, Expression e, Tokenizer.Token t, List<Value> params)
     {
         assertArgsOk(params, (fixedArgs) ->{
             if (fixedArgs)  // wrong number of args for fixed args
@@ -301,10 +301,13 @@ public class FunctionValue extends Value implements Fluff.ILazyFunction
         }
     }
 
-    public static List<LazyValue> lazify(List<Value> args)
-    {
-        List<LazyValue> lzargs = new ArrayList<>(args.size());
-        args.forEach( v -> lzargs.add( (c, t) -> v));
-        return lzargs;
+    @Override
+    public boolean pure() {
+        return false;
+    }
+
+    @Override
+    public boolean transitive() {
+        return false;
     }
 }

src/main/java/carpet/script/value/LazyListValue.java

@@ -192,6 +192,11 @@ public abstract class LazyListValue extends AbstractListValue implements Iterato
         return copy;
     }
 
+    @Override
+    public Value fromConstant() {
+        return (Value)clone();
+    }
+
     @Override
     public int hashCode()
     {

src/main/java/carpet/script/value/NBTSerializableValue.java

@@ -150,6 +150,11 @@ public class NBTSerializableValue extends Value implements ContainerValueInterfa
         return copy;
     }
 
+    @Override
+    public Value fromConstant() {
+        return deepcopy();
+    }
+
     // stolen from HopperBlockEntity, adjusted for threaded operation
     public static Inventory getInventoryAt(ServerWorld world, BlockPos blockPos)
     {

src/main/java/carpet/script/value/Value.java

@@ -244,4 +244,11 @@ public abstract class Value implements Comparable<Value>, Cloneable
     }
 
     public boolean isNull() { return false; }
+
+    /**
+     * @return retrieves useful in-run value of an optimized code-base value.
+     * For immutable values (most of them) it can return itself,
+     * but for mutables, it needs to be its copy or deep copy.
+     */
+    public Value fromConstant() { return this; }
 }