cppdraft_translate/cppdraft/sf/cmath/expint.md

[sf.cmath.expint]

29 Numerics library [numerics]

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

29.7.6 Mathematical special functions [sf.cmath]

29.7.6.15 Exponential integral [sf.cmath.expint]

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floating-point-type expint(floating-point-type x); float expintf(float x); long double expintl(long double x);

1

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

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Returns: Ei(x), where Ei is given by Formula 29.35 andx is x.

Ei(x)=−∫∞−xe−ttdt(29.35)