Re: problem with formatting large integers

[<jgiors@...>]

> -------- Original Message --------
> Date: Fri, 15 Apr 2011 22:25:36 -0500
> From: Javier Guerra Giraldez <javier@guerrag.com>
> Subject: Re: problem with formatting large integers
> To: Lua mailing list <lua-l@lists.lua.org>
> Message-ID: <BANLkTi=st1LfWWBiTYSD7RGPE5a_53vvtw@mail.gmail.com>
> Content-Type: text/plain; charset=UTF-8
> 
> On Fri, Apr 15, 2011 at 7:28 PM,  <jgiors@threeeyessoftware.com> wrote:
> > Point of note: The string.format code includes a cast from the floating
> > point format to the integer format (i.e. it's not just a detail of
> > sprintf).
> 
> to be specific:  on %i, it uses luaL_checkint(), which casts from
> lua_Integer to int.  since sprintf()'s %i assumes an int, to change it
> to a long, or long long would mean inserting one or two 'l's on the
> pattern before calling sprintf()
> 
> so it _is_ a detail of sprintf, because %i requires an int.
> 
> of course, the easiest solution is to just compile with a 64-bit int :-)
> 
> -- 
> Javier
> 

I think we're looking at this from different points of view. From my
point of view, string.format specifies format patterns which are often
parallel to, but not necessarily identical to the ones used by sprintf
(case in point: %q pattern which does not exist for sprintf). With this
view, Lua is free to translate %i into some other format which works for
the integer sizes Lua actually supports. A cast from floating point to
integer would be unnecessary.

If you take an alternate view that a string.format %i is necessarily
translated into an equivalent sprintf %i, then the cast is necessary and
there isn't really anything that can be done about Lua integers which
are outside the sprintf %i range.

John Giors
http://ThreeEyesSoftware.com
jgiors@ThreeEyesSoftware.com