ellint_fe

eve::ellint_fe = functor<ellint_fe_t>

inlineconstexpr

Header file

#include <eve/module/elliptic.hpp>

Callable Signatures

namespace eve
{
   // Regular overload
   constexpr auto ellint_fe(floating_value auto k)                                   noexcept; // 1
   constexpr auto ellint_fe(floating_value auto phi, floating_value auto k)          noexcept; // 2
   constexpr auto ellint_fe[modular](floating_value auto phi, floating_value auto alpha)noexcept; // 2
   constexpr auto ellint_fe[eccentric](floating_value auto phi, floating_value auto m)  noexcept; // 2
}

Parameters

• phi: floating Jacobi amplitude.
• k: floating elliptic modulus. k must satisfy $k^2\sin^2\phi \le 1$ or the result is NaN. In the complete case this means $|k| \le 1$.
• c: Conditional expression masking the operation.
• m: Logical value masking the operation.

Return value

1. the complete elliptic integral of the first and second kind $\mathbf{K}(k) = \int_0^{\pi/2} \frac{\mathrm{d}t}{\sqrt{1-k^2\sin^2 t}}$ and $\mathbf{E}(k) = \int_0^{\pi/2} \scriptstyle \sqrt{1-k^2\sin^2 t}\,\mathrm{d}t$ is returned. (corresponding to $\phi = \pi/2$) are returned.
2. the incomplete elliptic integral of the first kind is returned: $\mathbf{F}(\phi, k) = \int_0^{\phi} \frac{\mathrm{d}t}{\sqrt{1-k^2\sin^2 t}}$

Note

Be aware that as $\pi/2$ is not exactly represented by floating point values the result of the incomplete function with a $\phi$ floating point value representing $\pi/2$ can differ a lot with the result of the complete call.

External references

• C++ standard reference: ellint_fe
• DLMF: Elliptic Integrals
• Wolfram MathWorld: Elliptic Integral

Example

// revision 1
#include <eve/module/elliptic.hpp>
#include <iostream>
 
eve::wide wf{1.0, 0.0, 0.75, 0.5};
eve::wide wphi{1.0, 1.0e-30, 0.5, 0.0};
 
int main(){
   std::cout << "<- wf   = " << wf << "\n";
   std::cout << "<- wphi = " << wphi << "\n";
 
   std::cout << "-> ellint_fe(wf)                = " << eve::ellint_fe(wf) << "\n";
   std::cout << "-> ellint_fe(wphi, wf)          = " << eve::ellint_fe(wphi, wf) << "\n";
}