Hacker News Reader

Comment by gpderetta | Hacker News Reader

They are converted to bool in bool context. Outside of that you have to force it.

   int countNonZero = 0;
   for (int i = 0; i < values.size(); ++i) {
       countNonZero += !!values[i];
   }

Also c++ has explicit operator bool();

edit: not a great example as values[1] >0 would be better.

View on HN

You don't have to enforce a conversion from int to bool if you just want a bool. In this example you don't want to increment by 'bool', you want to increment by 1 or 0 (which are ints). So you use !!x to convert to bool and back to int.

The reason I'm pointing this out is that often enough I had to work with code where this distinction was unknown to the author and you come across code like if (!!x) which is, again, just nonsense.

edit: not a great example as values[1] >0 would be better.

Only if that's an array of unsigned ints, as otherwise the code would count only positive nonzeros.

You can also typecast to bool since C99. (bool)x if you include <stdbool.h> or (_Bool) if not.

Reply on news.ycombinator.com