double comp_ellint_1(double k);
float comp_ellint_1f(float k);
long double comp_ellint_1l(long double k);
Effects: These functions compute the complete elliptic integral of the first kind of their respective arguments k.
Returns: K(k) = F(k, π / 2), for |k| ≤ 1 where k is k.
See also [sf.cmath.ellint_1].