Solved

Just-for-fun II

Posted on 1998-08-25
2
223 Views
Last Modified: 2010-04-01
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
Comment
Question by:JYoungman
  • 2
2 Comments
 
LVL 11

Accepted Solution

by:
alexo earned 0 total points
ID: 1171175
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
 
LVL 11

Expert Comment

by:alexo
ID: 1171176
Did I?  It's hard to tell with 0 points ;-)
0

Featured Post

Master Your Team's Linux and Cloud Stack!

The average business loses $13.5M per year to ineffective training (per 1,000 employees). Keep ahead of the competition and combine in-person quality with online cost and flexibility by training with Linux Academy.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

When writing generic code, using template meta-programming techniques, it is sometimes useful to know if a type is convertible to another type. A good example of when this might be is if you are writing diagnostic instrumentation for code to generat…
Many modern programming languages support the concept of a property -- a class member that combines characteristics of both a data member and a method.  These are sometimes called "smart fields" because you can add logic that is applied automaticall…
The goal of the video will be to teach the user the difference and consequence of passing data by value vs passing data by reference in C++. An example of passing data by value as well as an example of passing data by reference will be be given. Bot…
The viewer will be introduced to the member functions push_back and pop_back of the vector class. The video will teach the difference between the two as well as how to use each one along with its functionality.

809 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question