Merge branch 'master' into 1.17

src/main/java/carpet/CarpetSettings.java

@@ -444,6 +444,19 @@ 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/script/CarpetScriptHost.java

@@ -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/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;
@@ -32,6 +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;
@@ -45,6 +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;
@@ -62,7 +66,7 @@ public class Expression
 
     public String getModuleName()
     {
-        return module == null?null:module.getName();
+        return module == null?"system chat":module.getName();
     }
 
     public void asATextSource()
@@ -86,6 +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();
@@ -139,13 +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
                 {
@@ -160,13 +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
                 {
@@ -180,13 +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
@@ -201,13 +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
                 {
@@ -222,13 +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
@@ -243,13 +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
                 {
@@ -312,6 +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)
@@ -330,6 +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())));
@@ -347,12 +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
@@ -367,12 +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
@@ -388,12 +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
                 {
@@ -451,7 +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);
@@ -474,7 +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);
@@ -599,16 +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)
@@ -675,19 +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
         {
@@ -715,35 +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)
                     {
@@ -757,47 +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

@@ -122,11 +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)

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

@@ -819,7 +819,7 @@ 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/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) ->
         {

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/FormattedTextValue.java

@@ -54,7 +54,7 @@ public class FormattedTextValue extends StringValue
 
     @Override
     public boolean getBoolean() {
-        return !text.asString().isEmpty();
+        return !text.getString().isEmpty();
     }
 
     @Override

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

@@ -152,6 +152,11 @@ 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; }
 }