Add RandomFunction and seed variable

src/main/java/com/dfsek/terra/generation/config/WorldGenerator.java

@@ -3,6 +3,7 @@ package com.dfsek.terra.generation.config;
 import com.dfsek.terra.config.genconfig.noise.NoiseConfig;
 import com.dfsek.terra.math.NoiseFunction2;
 import com.dfsek.terra.math.NoiseFunction3;
+import com.dfsek.terra.math.RandomFunction;
 import org.bukkit.World;
 import org.bukkit.block.data.BlockData;
 import org.polydev.gaea.biome.Generator;
@@ -36,12 +37,15 @@ public class WorldGenerator extends Generator {
     @SuppressWarnings({"rawtypes", "unchecked"})
     public WorldGenerator(long seed, String equation, String elevateEquation, Scope vScope, Map<String, NoiseConfig> noiseBuilders, Palette[] palettes, Palette[] slantPalettes, boolean preventSmooth) {
         Parser p = new Parser();
+        p.registerFunction("rand", new RandomFunction());
         Parser ep = new Parser();
+        ep.registerFunction("rand", new RandomFunction());
 
         Scope s = new Scope().withParent(vScope);
         xVar = s.create("x");
         yVar = s.create("y");
         zVar = s.create("z");
+        s.create("seed").setValue(seed);
 
         this.preventSmooth = preventSmooth;
 
@@ -63,6 +67,7 @@ public class WorldGenerator extends Generator {
             this.noiseExp = p.parse(equation, s).simplify();
             if(elevateEquation != null) {
                 Scope es = new Scope().withParent(vScope);
+                es.create("seed").setValue(seed);
                 this.elevationXVar = es.create("x");
                 this.elevationZVar = es.create("z");
                 this.elevationExp = ep.parse(elevateEquation, es).simplify();

src/main/java/com/dfsek/terra/math/RandomFunction.java

@@ -0,0 +1,30 @@
+package com.dfsek.terra.math;
+
+import org.polydev.gaea.util.FastRandom;
+import parsii.eval.Expression;
+import parsii.eval.Function;
+
+import java.util.List;
+
+/**
+ * Provides access to a PRNG ({@link org.polydev.gaea.util.FastRandom})
+ * <p>
+ * Takes 1 argument, which sets the seed
+ */
+public class RandomFunction implements Function {
+    @Override
+    public int getNumberOfArguments() {
+        return 1;
+    }
+
+    @Override
+    public double eval(List<Expression> list) {
+        long seed = (long) list.get(0).evaluate();
+        return new FastRandom(seed).nextDouble();
+    }
+
+    @Override
+    public boolean isNaturalFunction() {
+        return true;
+    }
+}