[chbot] C Challange #6

[Michael Pearce]

Actual output is

foo 20

the operator # causes the parameter to be replaced by a string literal

so mod(foo) becomes "foo"

and the xmod(foo)  uses the value of foo which gives "20"

Mike



On Thu, Sep 22, 2011 at 2:39 PM, Yani Dubin <yani.dubin at gmail.com> wrote:

> I would assume it printed "20 20". But then that seems too obvious and
> I must be missing some sort of tricky business around preprocessor
> operator precedence causing something funky?
>
> On Fri, Sep 23, 2011 at 9:12 AM, Andre Renaud <andre at bluewatersys.com>
> wrote:
> > Unfortunately, as I don't tend to attend the local meetings I won't be
> > able to back this up with a Chocolate Fish. However, who can give the
> > correct output for the following C program, with an explanation for why.
> >
> > #include <stdio.h>
> > #include <string.h>
> > #define xmod(s) mod(s)
> > #define mod(s) #s
> > #define foo 20
> >
> > int main(int argc, char *argv[])
> > {
> >  char buffer[20], buffer2[20];
> >
> >  strcpy(buffer, mod(foo));
> >  strcpy(buffer2, xmod(foo));
> >
> >  printf("%s %s\n", buffer, buffer2);
> >  return 0;
> > }
> >
> > Regards,
> > Andre
> >
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