std::sph_ne...ph_neumannl(3)

💖 NAME 💖

std::sph_neumann, std::sph_neumannf, std::sph_neumannl — std::sph_neumann, std::sph_neumannf, std::sph_neumannl

okay so welcome to the C++ Standard Library manual page for the std::sph_neumann / std::sph_neumannf / std::sph_neumannl besties 💅 (the page title is the truncated std::sph_ne...ph_neumannl(3), no cap, but we move). These are the spherical Neumann function girlies, and they are here to compute.

---

✨ Synopsis ✨

Defined in header <cmath> — and here’s the exact overload lineup, preserved in all its code-block glory:

Defined in header <cmath>

float       sph_neumann ( unsigned n, float x );
                                                                        (since C++17)
double      sph_neumann ( unsigned n, double x );
(until C++23)

long double sph_neumann ( unsigned n, long double x );
/* floating-point-type */ sph_neumann( unsigned n,
                                       /* floating-point-type  (1)
(since C++23)
*/ x );
float       sph_neumannf( unsigned n, float x );
(2) (since C++17)
long double sph_neumannl( unsigned n, long double x );
(3) (since C++17)

➕ Additional overloads

Additional overloads
Defined in header <cmath>

template< class Integer >
(A) (since C++17)
double      sph_neumann ( unsigned n, Integer x );

1-3) computes the spherical Bessel function of the second kind — also known as the spherical Neumann function — of n and x. 💖

The library provides overloads of std::sph_neumann for all cv-unqualified floating-point types as the type of the parameter x. (since C++23)

A) Additional overloads are provided for all integer types, which are treated as double.

---

🌸 Parameters 🌸

• n — the order of the function
• x — the argument of the function

---

🦋 Return value 🦋

If no errors occur, it returns the value of the spherical Bessel function of the second kind (spherical Neumann function) of n and x, that is:

n n(x) = (π/2x)1/2 N n+1/2(x)

where N n(x) is std::cyl_neumann(n, x) and x≥0.

---

🎀 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 n≥128, the behavior is implementation-defined

⚠️ bestie, that n≥128 line is a real caveat — implementation-defined behavior means the standard is not promising you a specific result there.

---

🧚 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.

The additional overloads are not required to be provided exactly as (A). They only need to be sufficient to ensure that for their argument num of integer type, std::sph_neumann(int_num, num) has the same effect as std::sph_neumann(int_num, static_cast<double>(num)).

---

🔥 Example 🔥

// Run this code

#include <cmath>
#include <iostream>

int main()
{
    // spot check for n == 1
    double x = 1.2345;
    std::cout << "n_1(" << x << ") = " << std::sph_neumann(1, x) << '\n';

    // exact solution for n_1
    std::cout << "-cos(x)/x² - sin(x)/x = "
              << -std::cos(x) / (x * x) - std::sin(x) / x << '\n';
}

Output

n_1(1.2345) = -0.981201
-cos(x)/x² - sin(x)/x = -0.981201

---

👀 See also 👀

• cyl_neumann, cyl_neumannf, cyl_neumannl — cylindrical Neumann functions (C++17) (function) (C++17) (C++17)
• sph_bessel, sph_besself, sph_bessell — spherical Bessel functions (of the first kind) (C++17) (function) (C++17) (C++17)

---

🌈 External links 🌈

Weisstein, Eric W. "Spherical Bessel Function of the Second Kind." From MathWorld — A Wolfram Web Resource.

---

source/version: http://cppreference.com · date: 2024.06.10 · page: std::sph_ne...ph_neumannl(3) — cute little footer sign-off, bestie, mwah 💋✨