Implement Math.random() purely in JavaScript.

src/math.js

Index: src/math.js
diff --git a/src/math.js b/src/math.js
index efab63a186d4f8b924894dad9c1f0be59ef9846a..8c26f31a5548b95e1e2eb97798787fb187d36627 100644
--- a/src/math.js
+++ b/src/math.js
@@ -174,8 +174,14 @@ function MathPow(x, y) {
 }
 
 // ECMA 262 - 15.8.2.14
+// random0 and random1 are initialized during genesis.
 function MathRandom() {
-  return %_RandomHeapNumber();
+  var r0 = (MathImul(18273, random0 & 0xFFFF) + (random0 >>> 16)) | 0;
+  random0 = r0;

[Michael Starzinger, 2013/11/11 14:11:12]

I am not sure about the sequence of the initialization here. Can we make sure
that "random0" and "random1" are bound to global variables by explicitly
declaring them at the top-level a few lines above? Thereby it is more obvious to
where these two variables are bound.

[Sven Panne, 2013/11/12 07:09:12]

Done.

+  var r1 = (MathImul(36969, random1 & 0xFFFF) + (random1 >>> 16)) | 0;
+  random1 = r1;
+  var x = ((r0 << 14) + (r1 & 0x3FFFF)) | 0;
+  return (x < 0 ? (x + 0x100000000) : x) / 0x100000000;
 }
 
 // ECMA 262 - 15.8.2.15