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'math.random' operates with integers when used for integer results

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(1 or 2 parameters)
This commit is contained in:
Roberto Ierusalimschy
2013-06-13 16:32:52 -03:00
parent 318575627f
commit 788b251157
1 changed files with 11 additions and 9 deletions
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20
lmathlib.c
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@@ -1,5 +1,5 @@
/* /*
** $Id: lmathlib.c,v 1.85 2013/05/06 17:22:55 roberto Exp $ ** $Id: lmathlib.c,v 1.86 2013/05/26 13:45:24 roberto Exp roberto $
** Standard mathematical library ** Standard mathematical library
** See Copyright Notice in lua.h ** See Copyright Notice in lua.h
*/ */
@@ -204,26 +204,28 @@ static int math_random (lua_State *L) {
/* the `%' avoids the (rare) case of r==1, and is needed also because on /* the `%' avoids the (rare) case of r==1, and is needed also because on
some systems (SunOS!) `rand()' may return a value larger than RAND_MAX */ some systems (SunOS!) `rand()' may return a value larger than RAND_MAX */
lua_Number r = (lua_Number)(rand()%RAND_MAX) / (lua_Number)RAND_MAX; lua_Number r = (lua_Number)(rand()%RAND_MAX) / (lua_Number)RAND_MAX;
lua_Integer low, up;
switch (lua_gettop(L)) { /* check number of arguments */ switch (lua_gettop(L)) { /* check number of arguments */
case 0: { /* no arguments */ case 0: { /* no arguments */
lua_pushnumber(L, r); /* Number between 0 and 1 */ lua_pushnumber(L, r); /* Number between 0 and 1 */
break; return 1;
} }
case 1: { /* only upper limit */ case 1: { /* only upper limit */
lua_Number u = luaL_checknumber(L, 1); low = 1;
luaL_argcheck(L, (lua_Number)1.0 <= u, 1, "interval is empty"); up = luaL_checkinteger(L, 1);
lua_pushnumber(L, l_mathop(floor)(r*u) + (lua_Number)(1.0)); /* [1, u] */
break; break;
} }
case 2: { /* lower and upper limits */ case 2: { /* lower and upper limits */
lua_Number l = luaL_checknumber(L, 1); low = luaL_checkinteger(L, 1);
lua_Number u = luaL_checknumber(L, 2); up = luaL_checkinteger(L, 2);
luaL_argcheck(L, l <= u, 2, "interval is empty");
lua_pushnumber(L, l_mathop(floor)(r*(u-l+1)) + l); /* [l, u] */
break; break;
} }
default: return luaL_error(L, "wrong number of arguments"); default: return luaL_error(L, "wrong number of arguments");
} }
/* random integer in the interval [low, up] */
up++; /* change interval to [low, up) */
luaL_argcheck(L, up - low > 0, 1, "interval is empty");
lua_pushinteger(L, (lua_Integer)(r * (lua_Number)(up - low)) + low);
return 1; return 1;
} }