added in_slime_chunk, seed, add seed option to rand

src/main/java/carpet/script/CarpetExpression.java

@@ -102,6 +102,7 @@ import net.minecraft.world.chunk.Chunk;
 import net.minecraft.world.chunk.ChunkStatus;
 import net.minecraft.world.chunk.WorldChunk;
 import net.minecraft.world.dimension.DimensionType;
+import net.minecraft.world.gen.ChunkRandom;
 import net.minecraft.world.loot.context.LootContext;
 import net.minecraft.world.loot.context.LootContextParameters;
 import org.apache.commons.lang3.tuple.Pair;
@@ -607,6 +608,8 @@ public class CarpetExpression
      * <p>Numeric function, indicating hardness of a block.</p>
      * <h3><code>blast_resistance(pos)</code></h3>
      * <p>Numeric function, indicating blast_resistance of a block.</p>
+     * <h3><code>in_slime_chunk(pos)</code></h3>
+     * <p>Boolean indicating if the given block position is in a slime chunk.</p>
 
      * <h3><code>top(type, pos)</code></h3>
      * <p>Returns the Y value of the topmost block at given x, z coords (y value of a block is not important), according to the
@@ -1018,6 +1021,19 @@ public class CarpetExpression
         this.expr.addLazyFunction("blast_resistance", -1, (c, t, lv) ->
                 genericStateTest(c, "blast_resistance", lv, (s, p, w) -> new NumericValue(s.getBlock().getBlastResistance())));
 
+        this.expr.addLazyFunction("in_slime_chunk", -1, (c, t, lv) ->
+        {
+            BlockPos pos = BlockValue.fromParams((CarpetContext)c, lv, 0).block.getPos();
+            ChunkPos chunkPos = new ChunkPos(pos);
+            Value ret = new NumericValue(ChunkRandom.create(
+                    chunkPos.x, chunkPos.z,
+                    ((CarpetContext)c).s.getWorld().getSeed(),
+                    987234911L
+            ).nextInt(10) == 0);
+            return (_c, _t) -> ret;
+        });
+
+
         this.expr.addLazyFunction("top", -1, (c, t, lv) ->
         {
             String type = lv.get(0).evalValue(c).getString().toLowerCase(Locale.ROOT);
@@ -2957,6 +2973,8 @@ public class CarpetExpression
      * loop(1000,game_tick())  // runs the game as fast as it can for 1000 ticks
      * loop(1000,game_tick(100)) // runs the game twice as slow for 1000 ticks
      * </pre>
+     * <h3><code>seed()</code></h3>
+     * <p>Returns current world seed.</p>
      * <h3><code>current_dimension()</code></h3>
      * <p>Returns current dimension that the script runs in.</p>
      * <h3><code>in_dimension(smth, expr)</code></h3>
@@ -3399,6 +3417,12 @@ public class CarpetExpression
             return (cc, tt) -> Value.TRUE;
         });
 
+        this.expr.addLazyFunction("seed", -1, (c, t, lv) -> {
+            ServerCommandSource s = ((CarpetContext)c).s;
+            Value ret = new NumericValue(s.getWorld().getSeed());
+            return (cc, tt) -> ret;
+        });
+
         this.expr.addLazyFunction("current_dimension", 0, (c, t, lv) -> {
             ServerCommandSource s = ((CarpetContext)c).s;
             Value retval = new StringValue(NBTSerializableValue.nameFromRegistryId(Registry.DIMENSION.getId(s.getWorld().dimension.getType())));

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

@@ -2720,12 +2720,15 @@ public class Expression
      * length('foo') => 3
      * </pre>
      *
-     * <h3><code>rand(expr)</code></h3>
+     * <h3><code>rand(expr), rand(expr, seed)</code></h3>
      * <p>returns a random number from <code>0.0</code>
      * (inclusive) to <code>expr</code> (exclusive).
      * In boolean context (in conditions, boolean functions, or <code>bool</code>), returns
      * false if the randomly selected value is less than 1. This means that <code>rand(2)</code> returns true half
-     * of the time and <code>rand(5)</code> returns true for 80% (4/5) of the time</p>
+     * of the time and <code>rand(5)</code> returns true for 80% (4/5) of the time. If seed is not provided, uses a random seed.
+     * If seed is provided, each consecutive call to rand() will act like 'next' call to the same random object.
+     * Scarpet keeps track of up to 1024 custom random number generators, so if you exceed this number (per app), then your
+     * random sequence will revert to the beginning.</p>
      * <pre>
      * map(range(10), floor(rand(10))) =&gt; [5, 8, 0, 6, 9, 3, 9, 9, 1, 8]
      * map(range(10), bool(rand(2))) =&gt; [1, 1, 1, 0, 0, 1, 1, 0, 0, 0]
@@ -2982,7 +2985,12 @@ public class Expression
         addUnaryFunction("type", v -> new StringValue(v.getTypeString()));
 
         addUnaryFunction("length", v -> new NumericValue(v.length()));
-        addLazyFunction("rand", 1, (c, t, lv) -> {
+        addLazyFunction("rand", -1, (c, t, lv) -> {
+            int argsize = lv.size();
+            Random randomizer = Expression.randomizer;
+            if (argsize != 1 && argsize != 2)
+                throw new InternalExpressionException("'rand' takes one (range) or two arguments (range and seed)");
+            if (argsize == 2) randomizer = c.host.getRandom(NumericValue.asNumber(lv.get(1).evalValue(c)).getLong());
             Value argument = lv.get(0).evalValue(c);
             if (argument instanceof ListValue)
             {

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

@@ -4,11 +4,13 @@ import carpet.script.bundled.Module;
 import carpet.script.exception.InternalExpressionException;
 import carpet.script.value.FunctionValue;
 import carpet.script.value.Value;
+import it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap;
 import it.unimi.dsi.fastutil.objects.Object2ObjectOpenHashMap;
 
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Random;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.function.Predicate;
 import java.util.stream.Stream;
@@ -16,6 +18,14 @@ import java.util.stream.Stream;
 public abstract class ScriptHost
 {
     public static Map<Value, Value> systemGlobals = new ConcurrentHashMap<>();
+    private static Map<Long, Random> randomizers = new Long2ObjectOpenHashMap<>();
+
+    public Random getRandom(long aLong)
+    {
+        if (randomizers.size() > 1024)
+            randomizers.clear();
+        return randomizers.computeIfAbsent(aLong, Random::new);
+    }
 
 
     public static class ModuleData