"double complex cproj(double complex "z");"
"float complex cprojf(float complex "z");"
"long double complex cprojl(long double complex "z");"
With this function you can project a point in the plane onto the surface of a Riemann Sphere, the one-point compactification of the complex plane. Each finite point z projects to z itself. Every complex infinite values is projected to a single infinite value, namely to positive infinity on the real axis.