Thread: a good idea

this is a very simple programe,but the last line "printf" is very clever.

Code:

main()
{
    int a,b,c,count=0;
    printf("There are different methods for XM to distribute books to 3 readers:\n");
    for(a=1;a<=5;a++)
       for(b=1;b<=5;b++)
           for(c=1;a!=b&&c<=5;c++)
               if(c!=a&&c!=b)
                  printf(count%4?"%2d:%d,%d,%d  " : "%2d:%d,%d,%d\n",++count,a,b,c);}

do you think so?

I believe that causes undefined behaviour. You don't know if

Code:

count%4?"%2d:%d,%d,%d  " : "%2d:%d,%d,%d\n"

will be evaluated before

Code:

++count

In order to avoid undefined behaviour you could simply (starting count at 1)

Code:

printf("%2d:%d,%d,%d", count, a, b, c);
printf(count++ % 4 ? "\n" : "   ");}

Of course, the best way is for your code to be readable, not save lines. If you want to save lines in main() just make a function with the desired behaviour. I once made newl() that prints("\n"). You could make a newl(int) to simulate the above behaviour.

Originally Posted by C_ntua

I believe that causes undefined behaviour. You don't know if

Code:

printf("%2d:%d,%d,%d", count, a, b, c);
printf(count++ % 4 ? "\n" : "   ");}

you are right
thank you ! but it should in this way

Code:

printf("%2d:%d,%d,%d", count, a, b, c);
            printf(count++%4?"  " :"\n");

Originally Posted by luoyangke

you are right
thank you ! but it should in this way

Code:

printf("%2d:%d,%d,%d", count, a, b, c);
            printf(count++%4?"  " :"\n");

Obfuscating your code will get you fired from most jobs.

I agree it is generally not a good idea. But, as always, it depends. For example this:

Code:

printf(count++%4?"  " :"\n");

is less clear than this

Code:

if (count++ % 4) 
   printf("   "); 
else 
   printf("\n");

but the second needs 4 lines, which might make things worse.

For example imagine a piece of code with a lots of ifs and elses. Adding one more which does a really minor thing might be worse than adding everything in one line. Because if you wanted to review your code for errors you would just read "prints something", since printf() is far less likely to cause errors. But if you add another if-then-else branch then you would read "if this print sth else print sth"

So it depends from the overal code...