pls explain this macro

[Ravi]

#define JOIN(s1,s2) printf("%s = %s %s = %s",#s1,s1,#s2,s2)

 

[Ian Collins]

#define JOIN(s1,s2) printf("%s = %s %s = %s",#s1,s1,#s2,s2)

What's "pls"? Please put your question in your message body.

Have you tried the macro? Your C book should explain the operation of #
on a macro argument.

 

[santosh]

"]
#define JOIN(s1,s2) printf("%s = %s %s = %s",#s1,s1,#s2,s2)[/QUOTE]

The name JOIN is rather misleading. The # preprocessor operator
causes it's accompanying argument to be "stringised", i.e., for it
to enclosed within double quotes before further processing.

So in your case, if you write:

JOIN(str1, str2)

the replacement token would be:

printf("%s = %s %s = %s", "str1", str1, "str2", str2);

 

[Richard Heathfield]

santosh said:

"]
#define JOIN(s1,s2) printf("%s = %s %s = %s",#s1,s1,#s2,s2)

The name JOIN is rather misleading. The # preprocessor operator
causes it's accompanying argument to be "stringised", i.e., for it
to enclosed within double quotes before further processing.

So in your case, if you write:

JOIN(str1, str2)

the replacement token would be:

printf("%s = %s %s = %s", "str1", str1, "str2", str2);[/QUOTE]

Not quite. It would be:

printf("%s = %s %s = %s","str1",str1,"str2",str2)

The most important difference is, of course, that your semicolon is
spurious.

 

[santosh]

"]
santosh said:

"]
#define JOIN(s1,s2) printf("%s = %s %s = %s",#s1,s1,#s2,s2)

[/QUOTE][/QUOTE]
[ ... ]

Not quite. It would be:

printf("%s = %s %s = %s","str1",str1,"str2",str2)
Yes!

The most important difference is, of course, that your semicolon is
spurious.

Indeed. I'd meant to write:

JOIN(str1, str2);