I saw a line of C that looked like this:
!ErrorHasOccured() ??!??! HandleError();
It compiled correctly and seems to run ok. It seems like it's checking if an error has occurred, and if it has, it handles it. But I'm not really sure what it's actually doing or how it's doing it. It does look like the programmer is trying express their feelings about errors.
I have never seen the ??!??!
before in any programming language, and I can't find documentation for it anywhere. (Google doesn't help with search terms like ??!??!
). What does it do and how does the code sample work?
??!
is a trigraph that translates to|
. So it says:which, due to short circuiting, is equivalent to:
Guru of the Week (deals with C++ but relevant here), where I picked this up.
Possible origin of trigraphs or as @DwB points out in the comments it's more likely due to EBCDIC being difficult (again). This discussion on the IBM developerworks board seems to support that theory.
From ISO/IEC 9899:1999 ยง5.2.1.1, footnote 12 (h/t @Random832):