is if(s.length()) saying that if it returns a value, proceed?

Question

Typically, I see code with say if(s.length() > 1) ..., but here it only has if(s.length()).

The length function is implemented as mentioned below. When used in the test3 function call within the file containing int main(), is if(s.length) saying that if it returns a count that is greater than zero then it will execute the body of that if statement?

int statistician::length() const
{
    return count;
}

Code (test3() call in int main()):

statistician s, t, u, v;

if (s.length( ) || t.length( )) return 0; // <-- HERE
if (s.sum( ) || t.sum( )) return 0;

t.next(5);
u.next(0); u.next(10); u.next(10); u.next(20);

v = s + s;
if (v.length( ) || v.sum( )) return 0;
v = s + u;
if (!(u == v)) return 0;
v = t + s;