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);

1
#

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

2
#

Returns:

Ei(x)=−∫∞−xe−ttdt

where x is x.