Re: 5.2 feature list?

[Glenn Maynard <glenn@...>]

On Mon, Oct 02, 2006 at 10:29:16AM -0700, Sam Roberts wrote:
> On Mon, Oct 02, 2006 at 07:05:17AM -0400, John Belmonte wrote:
> > Doug Currie wrote:
> > > So, my request is that Lua 5.2 either
> > > - apply tostring() to non-string "%s" arguments of string.format(), or
> > > - add a string.format option that applies tostring() to its argument,
> > > and then performs the usual "%s" action.
> > 
> > I'd like to see the first implemented by having lua_tostring honor
> > __tostring, and perhaps adding a lua_rawtostring if there is really
> > demand for it.
> 
> I don't think that can be done. Remember, lua_tostring converts the Lua
> value at the given index to a string.
> 
> So, calling lua_tostring() on a value that had a __tostring metamethod
> would remove it from the stack, replacing it with a string. Some people
> already don't like auto-coercions between number and string, can you
> imagine the trouble it would cause to have your user-data auto-coerced
> to strings? :-(

Hmm, a thought: if automatic coercion for numbers was also done via this
metamethod, then you could turn them off by removing the metamethod.

(If both exist, I'd think "metamethod for tostring()" and "metamethod
for implicit coercions" would be separate metamethods, since they're
entirely different operations.)

-- 
Glenn Maynard