luaV_tonumber
if (luaV_tonumber(p1, &temp) == NULL)
if ((b = luaV_tonumber(rb, &tempb)) != NULL &&
(c = luaV_tonumber(rc, &tempc)) != NULL) {
#define tonumber(o,n) (ttisnumber(o) || (((o) = luaV_tonumber(o,n)) != NULL))
LUAI_FUNC const TValue *luaV_tonumber (const TValue *obj, TValue *n);