Boolean in C

sierdzio

@sierdzio
If one has to include a header file for them, makes me wonder if they are not "part of the language", just should be available if you include the header. Are they just #defines in that file??

yup :D

#define and    &&
#define and_eq &=
#define bitand &
#define bitor  |
#define compl  ~
#define not    !
#define not_eq !=
#define or     ||
#define or_eq  |=
#define xor    ^
#define xor_eq ^=

They are not actual C++ language reserved keywords.

JonB

@sierdzio
Hmmmm.... So does gcc have these in some header file, or does their C++ actually have them as reserved? It does have an iso646.h file, with the #defines, yet you said they worked for you in gcc without you explicitly including that? Does it include it automatically or from something else?

J.Hilk

@JonB said in Boolean in C:

worked for you in gcc without you explicitly including that? Does it include it automatically or from something else

This header was originally in the C standard library as <iso646.h>.
Compatibility header, in C defines alternative operator representations which are keywords in C++.
This means that in a conforming implementation, including this header has no effect.

gcc has mostly a conforming implementation, at least in this regard

JonB

@J-Hilk said in Boolean in C:

This header was originally in the C standard library as <iso646.h>.

So what file is this in, which you say is included automatically?

jsulm

@JonB said in Boolean in C:

which you say is included automatically?

My understanding is that it is NOT included automatically in conforming C++ implementations because those understand these words as keywords and don't need this header file (which is only there for compatibility reasons).

J.Hilk

@JonB I'm talking about the iso646.h @sierdzio mentioned

https://en.cppreference.com/w/cpp/header/ciso646

Probably the reason why MSVC doesn't have those as keywords but requires this header is, IIRC, that it doesn't have/use a dedicated c compiler for c headers and it would break legacy stuff if those were used as keywords

JonB

@jsulm
Mine too. But I quote from @sierdzio above:

Last time I tried was last year. Clang, GCC all are 100% fine with it, MSVC was throwing errors.

I now see it's supposed to be defined in some iso646.h header, I never included it, perhaps that's the reason.

My question is (should be) aimed at him: he says it worked automatically in GCC/Clang (but not MSVC) with no #include from him, that's what I'm trying to understand.

fcarney

I know Boolean is someone's name.
But it kind of look like a diet fad to scare people skinny: boo-lean.

jsulm

@fcarney You mean Anne Boleyn, one of the wifes of king Henry VI which was executed. She was mother of Elisabeth I :-)

jeremy_k

@jsulm said in Boolean in C:

@fcarney You mean Anne Boleyn, one of the wifes of king Henry VI which was executed. She was mother of Elisabeth I :-)

Ha! I'm not sure what a Boleyn variable would be. Dangerous in some manner.

Presumably @fcarney is referring to George Boole.

Kent-Dorfman

@J-Hilk said in Boolean in C:

are you guys aware, that not is a valid keyword in c++ ?

Heretic!
and the discussion is about C. ;^P

But to the point about superfluous comparisons: I guess is comes down to whether you understand the grammar. If you understand that all comparison operations evaluate to a boolean value (zero, or not zero) then it should become evident that explicit comparisons of booleans to a constant is redundant.

Kent-Dorfman

@jeremy_k said in Boolean in C:

Ha! I'm not sure what a Boleyn variable would be. Dangerous in some manner.

I guess technically I AM, being a decendent of Mary Boleyn...as for being dangerous... :^D

JonB

@Kent-Dorfman said in Boolean in C:

I guess technically I AM, being a decendent of Mary Boleyn

Are you also claiming to be a descendant of Henry VIII? :)

Kent-Dorfman

@JonB said in Boolean in C:

Are you also claiming to be a descendant of Henry VIII? :)

Claiming is such a strict definition. It is an interesting possibility that historians play with, and I cannot discount how much my cousins look like Henry in his later years (according to paintings)...and we do know that grammy Mary was quite the party girl.