What is ':-!!' in C?

 

In C, :-!! is a sequence of operators that is often used as a trick to convert a value into a boolean representation (0 or 1) using bitwise negation and logical negation.

The !! operator is used to convert a value to its corresponding boolean representation, where any non-zero value becomes 1 (true) and zero becomes 0 (false).

The :- operator is not a standard operator in C. It's used in combination with !! to achieve this conversion.

Here's how it works:

c

#include <stdio.h>

int main() {
    int num = 42;
    int result = :-!!num; // Convert num to boolean representation

    printf("Original num: %d\n", num);
    printf("Boolean representation: %d\n", result);

    return 0;
}

Please note that the :- operator is not a standard C operator, and this usage is more of a trick than a recommended practice. Using explicit logical comparisons would be more readable and maintainable.