Add range option to PseudoRandom:next()

2 files changed, 17 insertions, 3 deletions

diff --git a/doc/lua_api.txt b/doc/lua_api.txt
index ae6771be5..68fbcee8c 100644
--- a/doc/lua_api.txt
+++ b/doc/lua_api.txt
@@ -632,7 +632,10 @@ methods:
 PseudoRandom: A pseudorandom number generator
 - Can be created via PseudoRandom(seed)
 methods:
-- next(): return next random number [0...32767]
+- next(): return next integer random number [0...32767]
+- next(min, max): return next integer random number [min...max]
+                  (max - min) must be 32767 or <= 6553 due to the simple
+                  implementation making bad distribution otherwise.
 
 Registered entities
 --------------------
diff --git a/src/scriptapi.cpp b/src/scriptapi.cpp
index 944b81a5e..70ca6c86a 100644
--- a/src/scriptapi.cpp
+++ b/src/scriptapi.cpp
@@ -3157,12 +3157,23 @@ private:
 		return 0;
 	}
 
-	// next(self) -> get next value
+	// next(self, min=0, max=32767) -> get next value
 	static int l_next(lua_State *L)
 	{
 		LuaPseudoRandom *o = checkobject(L, 1);
+		int min = 0;
+		int max = 32767;
+		lua_settop(L, 3); // Fill 2 and 3 with nil if they don't exist
+		if(!lua_isnil(L, 2))
+			min = luaL_checkinteger(L, 2);
+		if(!lua_isnil(L, 3))
+			max = luaL_checkinteger(L, 3);
+		if(max - min != 32767 && max - min > 32767/5)
+			throw LuaError(L, "PseudoRandom.next() max-min is not 32767 and is > 32768/5. This is disallowed due to the bad random distribution the implementation would otherwise make.");
 		PseudoRandom &pseudo = o->m_pseudo;
-		lua_pushinteger(L, pseudo.next());
+		int val = pseudo.next();
+		val = (val % (max-min+1)) + min;
+		lua_pushinteger(L, val);
 		return 1;
 	}