trigraphs ????

[Ingo Krabbe]

>
> Is trigraphs used for something ????
>
I think they have been used for something but are not very usefull in our
days. Trigrpahs should achieve extending some charactersets which don't
have some characters. Anyway there has to be some reason why ISO once has
introduced these sequences.

Excerpt from gcc manual:
=================================== snip
       -trigraphs
           Process ISO standard trigraph sequences.  These are
           three-character sequences, all starting with ??, that
           are defined by ISO C to stand for single characters.
           For example, ??/ stands for \, so '??/n' is a charac-
           ter constant for a newline.  By default, GCC ignores
           trigraphs, but in standard-conforming modes it con-
           verts them.  See the -std and -ansi options.

           The nine trigraph sequences are

           ??( -> [

           ??) -> ]

           ??< -> {

           ??> -> }

           ??= -> #

           ??/ -> \

           ??' -> ^

           ??! -> |

           ??- -> ~

           Trigraph support is not popular, so many compilers do
           not implement it properly.  Portable code should not
           rely on trigraphs being either converted or ignored.

=================================== snip