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better precision for log(x, 10)

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This commit is contained in:
Roberto Ierusalimschy 2009-02-18 10:06:05 -03:00
parent d07abcc6c7
commit 8975739839
1 changed files with 10 additions and 4 deletions
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14
lmathlib.c
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@ -1,5 +1,5 @@
/*
** $Id: lmathlib.c,v 1.69 2007/03/27 12:37:00 roberto Exp roberto $
** $Id: lmathlib.c,v 1.70 2007/06/21 13:48:04 roberto Exp roberto $
** Standard mathematical library
** See Copyright Notice in lua.h
*/
@ -112,9 +112,15 @@ static int math_pow (lua_State *L) {
}
static int math_log (lua_State *L) {
lua_Number res = log(luaL_checknumber(L, 1));
if (!lua_isnoneornil(L, 2))
res /= log(luaL_checknumber(L, 2));
lua_Number x = luaL_checknumber(L, 1);
lua_Number res;
if (lua_isnoneornil(L, 2))
res = log(x);
else {
lua_Number base = luaL_checknumber(L, 2);
if (base == 10.0) res = log10(x);
else res = log(x)/log(base);
}
lua_pushnumber(L, res);
return 1;
}