commenting out 'cout' using preprocessor macro

[qazmlp]

I hope comp.lang.c will not find the following question as a
complete off-topic.

I would like to remove ie.comment out the 'cout' statements during
compilation(act ually preprocessing) time.
The statements like this:
cout<<"somethin g\n" ;
should be made as
// cout<<"somethin g\n" ;
I tried for the following. But, It doesn't seem to be working.
//--------START
#ifdef DEBUG
#define COUT std::cout
#else
#define COUT \/\/
#endif

int main()
{
COUT<<"HELLO\n" <<std::endl ;
}

//--------END
If you can solve the above problem, please suggest a way for taking
care of
commenting out the 'cout' statements that spans in more than 1 line.
eg:

12 COUT<<"HELLO\n"
13 <<"WORLD\n" ;

[Allan Bruce]

"qazmlp" <qa********@red iffmail.com> wrote in message
news:db******** *************** ***@posting.goo gle.com...

I hope comp.lang.c will not find the following question as a
complete off-topic.

I would like to remove ie.comment out the 'cout' statements during
compilation(act ually preprocessing) time.
The statements like this:
cout<<"somethin g\n" ;
should be made as
// cout<<"somethin g\n" ;
I tried for the following. But, It doesn't seem to be working.
//--------START
#ifdef DEBUG
#define COUT std::cout
#else
#define COUT \/\/
#endif

int main()
{
COUT<<"HELLO\n" <<std::endl ;
}

//--------END
If you can solve the above problem, please suggest a way for taking
care of
commenting out the 'cout' statements that spans in more than 1 line.
eg:

12 COUT<<"HELLO\n"
13 <<"WORLD\n" ;

This is most definately a c++ question, but the same concept works in c.
The preprocessor directly copies across what you have in a define, so why
not just have
#define COUT //
Allan

[Jeff]

"qazmlp" <qa********@red iffmail.com> wrote in message
news:db******** *************** ***@posting.goo gle.com...

I hope comp.lang.c will not find the following question as a
complete off-topic.

I would like to remove ie.comment out the 'cout' statements during
compilation(act ually preprocessing) time.
The statements like this:
cout<<"somethin g\n" ;
should be made as
// cout<<"somethin g\n" ;

Sorry, it is off-topic here. cout is a part of C++, not C.

[snip]

--
Jeff

[Victor Bazarov]

"Jeff" <no****@notexis t.com> wrote...

"qazmlp" <qa********@red iffmail.com> wrote in message
news:db******** *************** ***@posting.goo gle.com...

I hope comp.lang.c will not find the following question as a
complete off-topic.

I would like to remove ie.comment out the 'cout' statements during
compilation(act ually preprocessing) time.
The statements like this:
cout<<"somethin g\n" ;
should be made as
// cout<<"somethin g\n" ;

Sorry, it is off-topic here. cout is a part of C++, not C.

Sorry, Jeff, statements explaining what is off-topic in
comp.lang.c are off-topic in comp.lang.c++. And give "qazmlp"
a break, he expressed his hope, didn't he?

Victor

[Victor Bazarov]

"Allan Bruce" <al*****@TAKEAW AYf2s.com> wrote...

[...]
This is most definately a c++ question, but the same concept works in c.
Why is it "definately " a C++ question? C has end-of-line comments.
Depending on how 'cout' is declared, it can be seen as a valid C
construct as well (just as in C++ I can declare it whatever I want
without including the <iostream>).. .
The preprocessor directly copies across what you have in a define, so why
not just have
#define COUT //

Why not? Simple. Comments are replaced with a single space char
before macro processing is ever begins. So, the directive you
wrote will be

#define COUT

after the phase 3 of the translation in both languages.

Victor

[Victor Bazarov]

"Derk Gwen" <de******@HotPO P.com> wrote...

# //--------START
# #ifdef DEBUG
# #define COUT std::cout
# #else
# #define COUT \/\/
# #endif

How about
#ifdef DEBUG
#define COUT if (1) std::cout
#else
#define COUT if (0) std::cout
#endif

If you optimise, the unexecutable code after if (0) should be excised.

# 12 COUT<<"HELLO\n"
# 13 <<"WORLD\n" ;

if (1) std::cout <<"HELLO\n"
<<"WORLD\n" ;

if (0) std::cout <<"HELLO\n"
<<"WORLD\n" ;

This approach has a major flaw. Imagine what this will expand into

if (somecondition)
COUT << "HELLO";
else
puts("condition is not met");

This is why it's better to use 'while' for that:

#ifdef WHATEVER
#define COUT std::cout
#else
#define COUT while(0) std::cout
#endif

However, that doesn't address the OP's concern that the code still
remains not compileable by a C compiler. It would be much better
to remove any reference to 'std::cout' whatsoever.

#ifdef __cplusplus
#define COUT std::cout
#else
#define COUT ????
#endif

I don't have a solution. The biggest problem in such case is how
you deal with user-define types that can be output using the C++
shift operator:

SomeUDT udt;
std::cout << udt; // is not uncommon in C++ programs

Making the whole statement invisible to the compiler (after the
preprocessing stage) is the task at hand (or at least how I see
it)...

Victor

[Alan Balmer]

On Fri, 8 Aug 2003 11:24:26 -0400, "Victor Bazarov"
<v.********@att Abi.com> wrote:

"Allan Bruce" <al*****@TAKEAW AYf2s.com> wrote...

[...]
This is most definately a c++ question, but the same concept works in c.

Why is it "definately " a C++ question? C has end-of-line comments.
Depending on how 'cout' is declared, it can be seen as a valid C
construct as well (just as in C++ I can declare it whatever I want
without including the <iostream>).. .

I'm curious - just how would you declare 'cout" to make

std::cout<<"HEL LO\n"<<std::end l ;

a valid C construct?

--
Al Balmer
Balmer Consulting
re************* ***********@att .net

[Victor Bazarov]

"Alan Balmer" <al******@att.n et> wrote...

On Fri, 8 Aug 2003 11:24:26 -0400, "Victor Bazarov"
<v.********@att Abi.com> wrote:

"Allan Bruce" <al*****@TAKEAW AYf2s.com> wrote...

[...]
This is most definately a c++ question, but the same concept works in

c.
Why is it "definately " a C++ question? C has end-of-line comments.
Depending on how 'cout' is declared, it can be seen as a valid C
construct as well (just as in C++ I can declare it whatever I want
without including the <iostream>).. .

I'm curious - just how would you declare 'cout" to make

std::cout<<"HEL LO\n"<<std::end l ;

a valid C construct?

I didn't say that the entire statement is a valid construct.
I said 'cout' could be a valid construct. To make 'cout' valid
all you need to do is

int cout;

In the context of the thread there was no requirement to make
'std::cout<<"HE LLO\n"<<std::en dl ;' a valid C construct.

Victor

[Victor Bazarov]

"Alan Balmer" <al******@att.n et> wrote...

On Fri, 8 Aug 2003 13:40:58 -0400, "Victor Bazarov"
<v.********@att Abi.com> wrote:

"Alan Balmer" <al******@att.n et> wrote...

On Fri, 8 Aug 2003 11:24:26 -0400, "Victor Bazarov"
<v.********@att Abi.com> wrote:

>"Allan Bruce" <al*****@TAKEAW AYf2s.com> wrote...
>> [...]
>> This is most definately a c++ question, but the same concept works

inc.

>
>Why is it "definately " a C++ question? C has end-of-line comments.
>Depending on how 'cout' is declared, it can be seen as a valid C
>construct as well (just as in C++ I can declare it whatever I want
>without including the <iostream>).. .

I'm curious - just how would you declare 'cout" to make

std::cout<<"HEL LO\n"<<std::end l ;

a valid C construct?

I didn't say that the entire statement is a valid construct.
I said 'cout' could be a valid construct. To make 'cout' valid
all you need to do is

int cout;

In the context of the thread there was no requirement to make
'std::cout<<"H ELLO\n"<<std::e ndl ;' a valid C construct.

Victor

The context of the thread was that you were contesting the statement
that the OP's question concerned C++.

No, I wasn't. That's something you just invented. The OP's question
concerns both C++ and C. Off-topicality of the OP's question in
comp.lang.c is what I was contesting.

Victor

[Samuele Armondi]

"qazmlp" <qa********@red iffmail.com> wrote in message
news:db******** *************** ***@posting.goo gle.com...

I hope comp.lang.c will not find the following question as a
complete off-topic.

I would like to remove ie.comment out the 'cout' statements during
compilation(act ually preprocessing) time.
The statements like this:
cout<<"somethin g\n" ;
should be made as
// cout<<"somethin g\n" ;
I tried for the following. But, It doesn't seem to be working.
//--------START
#ifdef DEBUG
#define COUT std::cout
#else
#define COUT \/\/
#endif

int main()
{
COUT<<"HELLO\n" <<std::endl ;
}

//--------END
If you can solve the above problem, please suggest a way for taking
care of
commenting out the 'cout' statements that spans in more than 1 line.
eg:

12 COUT<<"HELLO\n"
13 <<"WORLD\n" ;

Maybe you could create your own stream and use that as cout, i.e
#if !defined(DEBUG) && defined(__cplus plus)
class MyStream : public std::ostream \
{ \
template <class T> \
MyStream& operator << (const T& obj) \
{ return *this; } \
}; \
#define COUT MyStream
#else
#define COUT std::cout
#endif
I'm not sure if the above code will work, I'm especially not too sure about
the template bit. And it most definitely would not work on c systems! Maybe
you could define cout to be an int and the << operator to be + , i.e
#if !defined(DEBUG) && !defined(__cplu splus)
int bogus_cout;
#define COUT bogus_cout=
#define << +
#elif !defined(DEBUG) && defined(__cplus plus)
class MyStream : public std::ostream \
{ \
template <class T> \
MyStream& operator << (const T& obj) \
{ return *this; } \
}; \
#define COUT MyStream
#else
#define COUT std::cout
#endif
But you would need to be 100% sure that the code in question does not use
the << _anywhere_. Hope this helps anyway!
S. Armondi