title: Why do isnan, isinf, and isfinite return an int and not a bool?
body: <p><a href="http://en.cppreference.com/w/cpp/numeric/math/isnan" rel="nofollow">isnan</a> returns an int... <code>nonzero value if arg is NaN, ​0​ otherwise</code>. Why doesn't it return a bool? This isn't some legacy stuff, it's new with C++11.</p>