Re: isprint/isgraph not strictly do-able in Lua

[Roberto Ierusalimschy <roberto@...>]

> The weasel words of the ISO C standard say:
> 
> "the term control character refers to a member of a locale-specific
> set of characters that are not printing characters."
> 
> Therefore one cannot, sadly, deduce that string.match(s, "%C") is the
> same as isprint.
> 
> (isgraph is the same as isprint, but is not true for the space character).
> 
> I plan to add isprint and isgraph to luaposix for this reason (in
> common with some other useful bits of the C standard library that are
> missing from the Lua standard libraries).

'%g' (isgraph) was added to Lua 5.2 (work 4 already has it). Isprint
is then equivalent to [%g ].

-- Roberto