字符和布尔表达式相加会导致布尔结果吗？

Question

In the following function

The statement s[i] + s[i] == c; results in either zero or one (Boolean result).

My question: will the above expression be converted to boolean expression? It is considering the value of s[i]

void func(char s[], int c)
{
    int i, j;
    for (i = j = 0; s[i] != '\0'; i++)
        if (s[i] != c)
            s[j++] = s[i] + s[i] == c;
    s[j] = '\0';
}

Answer 1

Your premise is incorrect. The expression s[i] + s[i]==c is equivalent to (s[i] + s[i]) == c . Therefore, it is not "addition of char and boolean expression".

The result is a boolean expression, but note that there is no primitive bool type in C. So this expression will be of type int , with a value of either 1 or 0 . So therefore, the value of s[j] will be either 1 or 0 .

Answer 2

There is no boolean type in C, at least not unless you dive into the mostly unused parts of the standard.

Expressions that, semantically speaking, have boolean values, are managed by the compiler as int s with value 1 (for true) and 0 (for false). You can then assign that value to a char , and it will be appropiately down-casted/demoted.

This:

char a, b, c;
a = (b == c);

Works like this:

char a, b, c;
a = (b == c) ? 1 : 0;

Both 1 and 0 are of integer type, demoted to char on assignment.