29 Numerics library [numerics]

29.9 Mathematical functions for floating-point types [c.math]

29.9.5 Mathematical special functions [sf.cmath]

29.9.5.14 Exponential integral [sf.cmath.expint]

double expint(double x); float expintf(float x); long double expintl(long double x);

Effects: These functions compute the exponential integral of their respective arguments x.

Returns:

where x is x.