Re: How to get isblank?

[Bruno Haible]

Reuben Thomas wrote:
> 2009/10/7 Eric Blake <address@hidden>:
> > Can we add a summary of this logic to the isblank.texi documentation, to
> > point people to better replacements?
> 
> Proposed patch:
> 
> diff --git a/doc/posix-functions/isblank.texi 
> b/doc/posix-functions/isblank.texi
> index 2547793..a4924c7 100644
> --- a/doc/posix-functions/isblank.texi
> +++ b/doc/posix-functions/isblank.texi
> @@ -16,3 +16,14 @@ Portability problems not fixed by Gnulib:
>  This function is missing on some platforms:
>  AIX 4.3.2, IRIX 6.5, OSF/1 5.1, Solaris 9, mingw.
>  @end itemize
> +
> +There is no module for isblank because, first, it has not often been
> +requested, and secondly, on all known platforms, in all predefined
> +locales, @code{isblank(c)} is probably equivalent to @code{(c == ' ' ||
> +c == '\t')}. Look at the glibc definition (in
> address@hidden/localedata/locales/i18n}): the "blank" characters are `\t',
> +` ', U+1680, U+180E, U+2000 to U+2006, U+2008 to U+200A, U+205F, U+3000,
> +and only the first two are present in a common 8-bit encoding. Hence,
> +instead of using this function, with platform dependent semantics, most
> +programs will either want the pure ASCII version (@code{c_isblank}) or
> +the Unicode aware version (@code{uc_is_blank}).

The doc is right. But instead of documenting the absence of a module, we
can as well implement it, with not much trouble.

I'll commit three patches:
  - new module ctype,
  - new module isblank,
  - documentation about the four alternative APIs.

Bruno