I read in a book that C++ provides additional operators to the usual &,|, and ! which are "and","or" and "not" respectively, plus they come with automatic short circuiting properties where applicable. I would like to use these operators in my code but for some reason the compiler interprets them as identifiers whenever i use them and throws an error. I'm using Visual C++ 2008 Express Edition with SP1. How do i activate these operators to use in my code. Thank you.
+2
A:
The traditional C++ spelling [*] (just like in C) is && for "logical", short-circuit and, || for "logical", short-circuit or. ! is "logical" not (of course it doesn't short-circuit: what ever would that mean?!-). The bitwise versions are &, |, ~.
According to the C++ standard, the spellings you like (and, or, and so on) should also be implemented, but apparently popular compilers disobey that rule. However you should be able to #include <ciso646> or #include <iso646.h> to hack around that via macros -- see this page, and if your favorite compiler is missing these header files, just create them the obvious way, i.e.,
#define and &&
#define or ||
and so on. (Kudos and gratitude to the commenters for making me research the issue better and find this out!)
Alex Martelli
2009-06-13 22:36:06
Recent versions of the C++ standard include spellings such as "and" and "or".
Greg Hewgill
2009-06-13 22:37:18
@Greg good point, added a footnote on the likely future standard (albeit of, more or less, just "academic" interest at this point in time;-).
Alex Martelli
2009-06-13 22:40:25
@ Alex: My bad, I didn't even notice those.Thanks for the correction.
gogole
2009-06-13 22:50:00
Charles Bailey
2009-06-13 22:51:57
@Charles: So it it that VC++ does not implement these? Could you show me how to access them please
gogole
2009-06-13 22:57:19
VC 2008 is not stricly compliant, see here: http://stackoverflow.com/questions/198402/missing-desired-features-in-visual-c/198671#198671
Charles Bailey
2009-06-13 23:07:16
MS just makes me wonder sometimes... geez. Thanks Charles for the information. I guess I'll have to wait till 2010 with my fingers crossed hoping MS finally implement it or change my IDE.
gogole
2009-06-13 23:15:25
The and, or, bitand etc. keywords are defined in the original 1998 C++ Standard - see section 2.4.
anon
2009-06-13 23:22:04
@Charles, thanks, let me edit the answer accordingly.
Alex Martelli
2009-06-13 23:28:21
+4
A:
If you want to have the 'and', 'or', 'xor', etc keyword versions of the operators made available in MSVC++ then you either have to use the '/Za' option to disable extensions or you have to include iso646.h.
Michael Burr
2009-06-13 23:18:58
Having made your day, I'd strongly suggest avoiding using the 'alternative tokens' for the operators. I think that most C++ programmers reading the code would prefer to see the usual operators.
Michael Burr
2009-06-13 23:30:34
gogole
2009-06-13 23:50:54
Personally, I don't think it helps understanding to use the words instead of the symbols. You'll still have to get a handle on the old style to read code other people write. And adding the choice to C++ doesn't add it to C, Java, C#, Objective-C, or JavaScript. And either way, you're going to have to get "bitwise" and "logical" straight or fall into some really hard-to-debug situations.
Nosredna
2009-06-14 00:18:06
I understand that it's a matter of opinion or style, but I think that people are used to the punctuation-style tokens and would find the keyword variants something they have to 'stop and think about'. I'm currently working a project where the existing code mostly uses macros for the logical operators (AND, OR, NEQ, etc), and I must say I don't like it at all... I believe the alternative keyword tokens were provided mostly to aid programmers with non-US keyboards that didn't always have the correct punctuation characters, not an attempt to make them more readable (just more type-able).
Michael Burr
2009-06-14 00:27:58
A benefit to using the symbol style is that it is easy to distinguish between operators and variables when scanning code. It's a lot harder when everything is alphanumeric text.
emddudley
2009-06-14 00:39:32
@emdduley, I agree with that for C-based languages. However, Ruby and Python use the words and manage to be readable. I think Perl gives you the choice.
Nosredna
2009-06-14 03:57:30
I've come across this style a few times and never liked it. Makes it difficult to tell whether the original writer intended logical or bitwise operations.
Dan O
2009-06-14 07:06:24
A different color for these tokens would solve all the issues you guys are complaining about. I must admit, using theses tokens with their colors indistinguishable from the actual code makes it a bit difficult to spot them. When they are implemented in VC++ and become keywords the different coloration (from black to blue) should make things easier.
gogole
2009-06-14 09:12:40