Re: [ANN] Lua 5.3.0 (beta) now available

[Roberto Ierusalimschy <roberto@...>]

> In lvm.h:
> 
>     #define tonumber(o,n) \
> (ttisfloat(o) ? (*(n) = fltvalue(o), 1) : luaV_tonumber_(o,n))
> 
> Yet `luaV_tonumber_` already handles this case.
> We could probably get rid of the #define altogether and just use
> `luaV_tonumber_`.
> 
> I'm also wondering why we gained the "_" suffix.

The define saves a function call in what we expect to be a common case
(using a float as a float). The suffix is a convention in Lua that a
function should not be called directly, only thourgh its corresponding
macro. The fact that luaV_tonumber_ handles floats is an implementation
detail, a consequence of its way of converting "integer strings" to
floats. It could as well be implemented like this:

int luaV_tonumber_ (const TValue *obj, lua_Number *n) {
  TValue v;
  if (ttisinteger(obj)) {
    *n = cast_num(ivalue(obj));
    return 1;
  }
  else if (cvt2num(obj) &&  /* string convertible to number? */
            luaO_str2num(svalue(obj), &v) == tsvalue(obj)->len + 1) {
    if (ttisinteger(&v))
      *n = cast_num(ivalue(&v));
    else
      *n = fltvalue(&v);
    return 1;
  }
  return 0;  /* conversion failed */
}

-- Roberto