Re: how the macro works

From:
=?Utf-8?B?R2Vvcmdl?= <George@discussions.microsoft.com>
Newsgroups:
microsoft.public.vc.language
Date:
Wed, 12 Dec 2007 04:58:00 -0800
Message-ID:
<FC3FA56D-53E0-4CE1-9527-095311DF1B53@microsoft.com>
Thanks Vladimir,

My question is,

I think using

#define GETFOO (Foo( &counter ), counter)

is the same as

#define GETFOO Foo( &counter )

So, no benefits of using , operator, right?

regards,
George

"Vladimir Grigoriev" wrote:

The original fucntion returns nothing (void). The macro helps after calling
the function also to get the result value of counter.
For example

// #define GETFOO ( Foo(&counter), counter)

std::cout << "GETFOO = " << GETFOO << std::endl;

Vladimir Grigoriev

"George" <George@discussions.microsoft.com> wrote in message
news:CC8911F2-CDC3-41C3-B26D-1B4B2A2717CC@microsoft.com...

Thanks Vladimir,

I do not understand how this statement works,

(Foo( &counter ), counter);

I have tested that the simple statement (without comment) also works. What
is the benefit and function to add , and counter in macro definition?

// #define GETFOO Foo((&counter), counter)
#define GETFOO Foo(&counter)

regards,
George

"Vladimir Grigoriev" wrote:

In the function Foo() the statement return is obsolete. So the valid code
of
the function looks like

void Foo (int* input)
{
   *input = 100;
}

The macro GETFOO uses operator ',' (comma). For the comma operator the
last
value in the list is the value of the operator in whole.
for example, for

int i = ( 2, 3);

i will be set to 3.

It is better to rewrite the function Foo() as

int Foo( int & input )
{
   input = 100;
   return ( input );
}

Vladimir Grigoriev

"George" <George@discussions.microsoft.com> wrote in message
news:AD5B3494-BD1F-4520-AF76-9F708CE66E36@microsoft.com...

Hello everyone,

I can not understand how the following code works and assign 100 to
counter
variable?

[Code]
void Foo (int* input)
{
*input = 100;

return;
}

#define GETFOO (Foo( &counter ), counter)

int counter;

int main()
{
GETFOO;
return 0;
}
[/Code]

thanks in advance,
George

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