std::atanh, std::atanhf, std::atanhl

Since C++26

Header: <cmath>

1-3) Computes the inverse hyperbolic tangent of num.The library provides overloads of std::atanh for all cv-unqualified floating-point types as the type of the parameter.(since C++23)

# Declarations

float atanh ( float num );
double atanh ( double num );
long double atanh ( long double num );

(until C++23)

/*floating-point-type*/
atanh ( /*floating-point-type*/ num );

(since C++23) (constexpr since C++26)

float atanhf( float num );

(since C++11) (constexpr since C++26)

long double atanhl( long double num );

(since C++11) (constexpr since C++26)

SIMD overload (since C++26)

template< /*math-floating-point*/ V >
constexpr /*deduced-simd-t*/<V>
atanh ( const V& v_num );

(since C++26)

Additional overloads (since C++11)

template< class Integer >
double atanh ( Integer num );

(constexpr since C++26)

# Parameters

num: floating-point or integer value

# Return value

If no errors occur, the inverse hyperbolic tangent of num (tanh-1(num), or artanh(num)), is returned.

# Notes

Although the C standard (to which C++ refers for this function) names this function “arc hyperbolic tangent”, the inverse functions of the hyperbolic functions are the area functions. Their argument is the area of a hyperbolic sector, not an arc. The correct name is “inverse hyperbolic tangent” (used by POSIX) or “area hyperbolic tangent”.

POSIX specifies that in case of underflow, num is returned unmodified, and if that is not supported, an implementation-defined value no greater than DBL_MIN, FLT_MIN, and LDBL_MIN is returned.

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::atanh(num) has the same effect as std::atanh(static_cast(num)).

# Example

#include <cerrno>
#include <cfenv>
#include <cfloat>
#include <cmath>
#include <cstring>
#include <iostream>
// #pragma STDC FENV_ACCESS ON
 
int main()
{
    std::cout << "atanh(0) = " << std::atanh(0) << '\n'
              << "atanh(-0) = " << std::atanh(-0.0) << '\n'
              << "atanh(0.9) = " << std::atanh(0.9) << '\n';
 
    // error handling
    errno = 0;
    std::feclearexcept(FE_ALL_EXCEPT);
 
    std::cout << "atanh(-1) = " << std::atanh(-1) << '\n';
 
    if (errno == ERANGE)
        std::cout << "    errno == ERANGE: " << std::strerror(errno) << '\n';
    if (std::fetestexcept(FE_DIVBYZERO))
        std::cout << "    FE_DIVBYZERO raised\n";
}