pls explain this macro | | |
#define JOIN(s1,s2) printf("%s = %s %s = %s",#s1,s1,#s2,s2)
| | | | re: pls explain this macro
Ravi wrote: Quote:
#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.
--
Ian Collins. | | | | re: pls explain this macro
On Wednesday 18 Jul 2007 1:53 pm, in comp.lang.c, Ravi
<ra.ravi.rav@gmail.comwrote:
Message ID: <1184747027.585196.289450@j4g2000prf.googlegroups. com> Quote:
#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); | | | | re: pls explain this macro
santosh said: Quote:
On Wednesday 18 Jul 2007 1:53 pm, in comp.lang.c, Ravi
<ra.ravi.rav@gmail.comwrote:
Message ID: <1184747027.585196.289450@j4g2000prf.googlegroups. com>
> Quote:
>#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);
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.
--
Richard Heathfield <http://www.cpax.org.uk>
Email: -www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999 | | | | re: pls explain this macro
On Wednesday 18 Jul 2007 3:12 pm, in comp.lang.c, Richard Heathfield
<rjh@see.sig.invalidwrote:
Message ID: <6fWdnewKTZl2QgDbRVnygwA@bt.com> Quote:
santosh said:
> Quote:
>On Wednesday 18 Jul 2007 1:53 pm, in comp.lang.c, Ravi
><ra.ravi.rav@gmail.comwrote:
>Message ID: <1184747027.585196.289450@j4g2000prf.googlegroups. com>
>> Quote:
>>#define JOIN(s1,s2) printf("%s = %s %s = %s",#s1,s1,#s2,s2)
[ ... ] Quote: Quote:
>So in your case, if you write:
>>
> JOIN(str1, str2)
>>
>the replacement token would be:
>>
> printf("%s = %s %s = %s", "str1", str1, "str2", str2);
>
Not quite. It would be:
>
printf("%s = %s %s = %s","str1",str1,"str2",str2)
Yes! Quote:
The most important difference is, of course, that your semicolon is
spurious.
Indeed. I'd meant to write:
JOIN(str1, str2); |  |
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