std::ellint_1, std::ellint_1f, std::ellint_1l

 

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Special mathematical functions

assoc_laguerreassoc_laguerrefassoc_laguerrel assoc_legendreassoc_legendrefassoc_legendrel betabetafbetal comp_ellint_1comp_ellint_1fcomp_ellint_1l comp_ellint_2comp_ellint_2fcomp_ellint_2l comp_ellint_3comp_ellint_3fcomp_ellint_3l cyl_bessel_icyl_bessel_ifcyl_bessel_il

cyl_bessel_jcyl_bessel_jfcyl_bessel_jl cyl_bessel_kcyl_bessel_kfcyl_bessel_kl cyl_neumanncyl_neumannfcyl_neumannl ellint_1ellint_1fellint_1l ellint_2ellint_2fellint_2l ellint_3ellint_3fellint_3l expintexpintfexpintl

hermitehermitefhermitel laguerrelaguerreflaguerrel legendrelegendreflegendrel riemann_zetariemann_zetafriemann_zetal sph_besselsph_besselfsph_bessell sph_legendresph_legendrefsph_legendrel sph_neumannsph_neumannfsph_neumannl

 

double      ellint_1( double k, double φ ); float       ellint_1f( float k, float φ  ); long double ellint_1l( long double k, long double φ );	(1)	(since C++17)
Promoted    ellint_1( Arithmetic k, Arithmetic φ );	(2)	(since C++17)

1) Computes the incomplete elliptic integral of the first kind of k and φ.

2) A set of overloads or a function template for all combinations of arguments of arithmetic type not covered by (1). If any argument has integral type, it is cast to double. If any argument is long double, then the return type Promoted is also long double, otherwise the return type is always double.

Parameters

k	-	elliptic modulus or eccentricity (a value of a floating-point or integral type)
φ	-	Jacobi amplitude (a value of floating-point or integral type, measured in radians)

Return value

If no errors occur, value of the incomplete elliptic integral of the first kind of k and φ, that is ∫φ
0

dθ

√1-k2 sin2 θ

, is returned.

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 |k|>1, a domain error may occur

Notes

Implementations that do not support C++17, but support ISO 29124:2010, provide this function 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.

Implementations that do not support ISO 29124:2010 but support TR 19768:2007 (TR1), provide this function in the header tr1/cmath and namespace std::tr1

An implementation of this function is also available in boost.math

Example

Run this code

#include <cmath>
#include <iostream>
int main()
{
    double hpi = std::acos(-1)/2;
    std::cout << "F(0,π/2) = " << std::ellint_1(0, hpi) << '\n'
              << "F(0,-π/2) = " << std::ellint_1(0, -hpi) << '\n'
              << "π/2 = " << hpi << '\n'
              << "F(0.7,0) = " << std::ellint_1(0.7, 0) << '\n';
}

Output:

F(0,π/2) = 1.5708
F(0,-π/2) = -1.5708
π/2 = 1.5708
F(0.7,0) = 0

External links

Weisstein, Eric W. "Elliptic Integral of the First Kind." From MathWorld--A Wolfram Web Resource.

See also

comp_ellint_1comp_ellint_1fcomp_ellint_1l (C++17)(C++17)(C++17)

(complete) elliptic integral of the first kind (function)