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Add range option to PseudoRandom:next()

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This commit is contained in:
Perttu Ahola 2012-03-28 21:16:47 +03:00
parent 9a1df7bf38
commit 68625b047f
2 changed files with 17 additions and 3 deletions
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5
doc/lua_api.txt
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@ -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
--------------------

15
src/scriptapi.cpp
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@ -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;
}