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std::expint, std::expintf, std::expintl

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Mathematical special functions
 
double      expint( double arg );

double      expint( float arg );
double      expint( long double arg );
float       expintf( float arg );

long double expintl( long double arg );
 (1)
double      expint( IntegralType arg );
 (2)
1) Computes the exponential integral of arg.
2) A set of overloads or a function template accepting an argument of any integral type. Equivalent to (1) after casting the argument to double.

As all special functions, expint is only guaranteed to be available in <cmath> if __STDCPP_MATH_SPEC_FUNCS__ is defined by the implementation to a value at least 201003L and if the user defines __STDCPP_WANT_MATH_SPEC_FUNCS__ before including any standard library headers.

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[edit] Parameters

arg - value of a floating-point or Integral type

[edit] Return value

If no errors occur, value of the exponential integral of arg, that is -∫∞
-arg
e-t
t
dt, is returned.

[edit] Error handling

Errors may be reported as specified in math_errhandling.

  • If the argument is NaN, NaN is returned and domain error is not reported.
  • If the argument is ±0, -∞ is returned.

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