Fixed math.randomseed() can't handle double values

- math.randomseed(os.time()) was seeding like math.randomseed(0)
- added unit tests

Author: Mangatome

Diff for: KopiLua/src/lmathlib.cs

@@ -205,8 +205,16 @@ private static int MathRandom (LuaState L) {
 
 
 		private static int MathRandomSeed (LuaState L) {
-		  //srand(luaL_checkint(L, 1));
-			rng = new Random(LuaLCheckInt(L, 1));
+            // math.randomseed() can take a double number but Random expects an integer seed.
+            // we use modulus to bring back the double to the allowed integer interval.
+            LuaNumberType seed = Math.Abs(LuaLCheckNumber(L, 1));
+            LuaNumberType max = (LuaNumberType)int.MaxValue;
+            while (seed > max)
+            {
+                seed = fmod(seed, max);
+            }
+
+			rng = new Random((int)seed);
 		  return 0;
 		}
 

Diff for: KopiLua/src/luaconf.cs

@@ -1137,8 +1137,7 @@ public static int strlen(CharPtr str)
 
 		public static lua_Number fmod(lua_Number a, lua_Number b)
 		{
-			float quotient = (int)Math.Floor(a / b);
-			return a - quotient * b;
+			return a - Math.Floor(a / b) * b;
 		}
 
 		public static lua_Number modf(lua_Number a, out lua_Number b)

Diff for: tests/core.cs

@@ -2,7 +2,8 @@
 using System;
 using NUnit.Framework;
 using System.IO;
-using KopiLua;
+using KopiLua;
+using System.Text;
 
 namespace Tests.iOS
 {
@@ -184,6 +185,16 @@ public void OSLib()
 
             // Test for os.difftime giving result in seconds.
             AssertString(st1 + "\n" + st2 + "\nassert(os.difftime(t2, t1) == 30)");
+        }
+
+        [Test]
+        public void MathLib()
+        {
+            // Test for math.random() giving different values after init with math.randomseed(os.time()).
+            AssertString("local s1 = os.time({year=2015, month=5, day=28, hour=15, min=50, sec=48})\nlocal s2 = s1 + 1\nmath.randomseed(s1)\nmath.random()\nmath.random()\nlocal n1 = math.random()\nmath.randomseed(s2)\nmath.random()\nmath.random()\nlocal n2 = math.random()\nprint(tostring(n1) .. ',' .. tostring(n2))\nassert(n1 ~= n2)");
+
+            // Test for math.random() giving same values for math.randomseed(42).
+            AssertString("math.randomseed(42)\nmath.random()\nmath.random()\nlocal n1 = math.random()\nmath.randomseed(42)\nmath.random()\nmath.random()\nlocal n2 = math.random()\nprint(tostring(n1) .. ',' .. tostring(n2))\nassert(n1 == n2)");
         }
 	}
 }