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  • Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 248
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Just-for-fun II

int plainc(void)
{
  switch (2 //**/ 2
         ) {
    case 2: return 0; /* actually C++ */
    default: return 1; /* plain C */
   }
}

Has anybody got another function which is valid in both languages that does the same job?
0
JYoungman
Asked:
JYoungman
  • 2
1 Solution
 
alexoCommented:
This only works if the C compiler is strict ANSI and does not treat "//" as a valid comment delimiter (a common extension).

However, Struostrup says (B.2.1) "ISO C is being revised to allow // as in C++" thus invalidating the technique.

A similar (and more readable) technique that is guaranteed to work is:

    int plainc(void) { return sizeof('a') == sizeof(int) ? 1 : 2; }

And a slightly more obscure one:

    int plainc(void)
    {
        int x;
        {
            struct x { int a, b; };
            return sizeof(x) == sizeof(int) ? 1 : 2;
        }
    }

And the most portable is, of course:

    int plainc(void)
    {
    #ifdef __cplusplus
        return 2;
    #else
        return 1;
    #endif
    }

Do I get an 'A' ?
0
 
alexoCommented:
Did I?  It's hard to tell with 0 points ;-)
0

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