C5. Exponential and logarithmic integrals

Functions
function	e1 (x::Real)
	Exponential integral E1(x)
function	ei (x::Real)
	Exponential integral Ei(x)
function	li (x::Real)
	Logarithmic integral li(x)

Detailed Description

This is the group of C5. Exponential and logarithmic integrals.