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math.random: use 'random' when available + changes to work correctly

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for any integer interval (up to [minint,maxint])
This commit is contained in:
Roberto Ierusalimschy 2014-04-10 14:53:33 -03:00
parent fdd137276b
commit 5336cc9d6a
1 changed files with 19 additions and 8 deletions
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27
lmathlib.c
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@ -21,6 +21,17 @@
#define PI (l_mathop(3.141592653589793238462643383279502884)) #define PI (l_mathop(3.141592653589793238462643383279502884))
#if !defined(l_rand) /* { */
#if defined(LUA_USE_POSIX)
#define l_rand() random()
#define l_srand(x) srandom(x)
#else
#define l_rand() rand()
#define l_srand(x) srand(x)
#endif
#endif /* } */
static int math_abs (lua_State *L) { static int math_abs (lua_State *L) {
if (lua_isinteger(L, 1)) { if (lua_isinteger(L, 1)) {
lua_Integer n = lua_tointeger(L, 1); lua_Integer n = lua_tointeger(L, 1);
@ -146,7 +157,7 @@ static int math_log (lua_State *L) {
res = l_mathop(log)(x); res = l_mathop(log)(x);
else { else {
lua_Number base = luaL_checknumber(L, 2); lua_Number base = luaL_checknumber(L, 2);
if (base == (lua_Number)10.0) res = l_mathop(log10)(x); if (base == 10.0) res = l_mathop(log10)(x);
else res = l_mathop(log)(x)/l_mathop(log)(base); else res = l_mathop(log)(x)/l_mathop(log)(base);
} }
lua_pushnumber(L, res); lua_pushnumber(L, res);
@ -219,10 +230,10 @@ static int math_max (lua_State *L) {
static int math_random (lua_State *L) { static int math_random (lua_State *L) {
/* 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 */
lua_Number r = (lua_Number)(rand()%RAND_MAX) / (lua_Number)RAND_MAX;
lua_Integer low, up; lua_Integer low, up;
lua_Number r = (lua_Number)l_rand() * (1.0 / ((lua_Number)RAND_MAX + 1.0));
if (r >= 1.0) /* can occur if lua_Number has no precision for RAND_MAX */
r = 0.0; /* statistically irrelevant; avoids out-of-range results */
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 */
@ -241,15 +252,15 @@ static int math_random (lua_State *L) {
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] */ /* random integer in the interval [low, up] */
up++; /* change interval to [low, up) */ luaL_argcheck(L, low <= up, 1, "interval is empty");
luaL_argcheck(L, up - low > 0, 1, "interval is empty"); r *= ((lua_Number)((lua_Unsigned)up - (lua_Unsigned)low) + 1.0);
lua_pushinteger(L, (lua_Integer)(r * (lua_Number)(up - low)) + low); lua_pushinteger(L, (lua_Integer)((lua_Unsigned)r + (lua_Unsigned)low));
return 1; return 1;
} }
static int math_randomseed (lua_State *L) { static int math_randomseed (lua_State *L) {
srand((unsigned int)luaL_checkunsigned(L, 1)); l_srand((unsigned int)luaL_checkunsigned(L, 1));
(void)rand(); /* discard first value to avoid undesirable correlations */ (void)rand(); /* discard first value to avoid undesirable correlations */
return 0; return 0;
} }