Acosh
Defined in header <cmath>
.
Description
Computes the inverse hyperbolic cosine of num
.
The library provides overloads of std::acosh for all cv-unqualified floating-point types as the type of the parameter num
(od C++23)
Additional Overloads are provided for all integer types, which are treated as double.
Declarations
- C++23
- C++11
// 1)
/* floating-point-type */ acosh( /* floating-point-type */ num );
// 2)
float acoshf( float num );
// 3)
long double acoshl( long double num );
// 4)
template< class Integer >
double acosh ( Integer num );
//1 )
float acosh ( float num );
// 2)
double acosh ( double num );
// 3)
long double acosh ( long double num );
// 4)
float acoshf( float num );
// 5)
long double acoshl( long double num );
// 6)
template< class Integer >
double acosh ( Integer num );
Parameters
num
- floating-point or integer value
Return value
If no errors occur, the inverse hyperbolic cosine of num
(cosh-1(num), or arcosh(num)) on the interval [0, +∞]
, is returned.
If a domain error occurs, an implementation-defined value is returned (NaN where supported).
Error handling
Errors are reported as specified in math_errhandling.
If the argument is less than 1
, a domain error occurs.
If the implementation supports IEEE floating-point arithmetic (IEC 60559):
if the argument is less than 1
, FE_INVALID is raised an NaN is returned
if the argument is 1
, +0
is returned
if the argument is +∞
, +∞
is returned
if the argument is NaN, NaN is returned
Notes
Although the C standard (to which C++ refers for this function) names this function "arc hyperbolic cosine", 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 cosine" (used by POSIX) or "area hyperbolic cosine".
The additional overloads are not required to be provided exactly as Additional Overloads.
They only need to be sufficient to ensure that for their argument num
of integer type,
std::acosh(num)
has the same effect as std::acosh(static_cast<double>(num))
.
Examples
#include <cerrno>
#include <cfenv>
#include <cfloat>
#include <cmath>
#include <cstring>
#include <iostream>
// #pragma STDC FENV_ACCESS ON
int main()
{
std::cout
<< "acosh(1) = "
<< std::acosh(1) << '\n'
<< "acosh(10) = "
<< std::acosh(10) << '\n'
<< "acosh(DBL_MAX) = "
<< std::acosh(DBL_MAX) << '\n'
<< "acosh(Inf) = "
<< std::acosh(INFINITY) << '\n';
// error handling
errno = 0;
std::feclearexcept(FE_ALL_EXCEPT);
std::cout
<< "acosh(0.5) = "
<< std::acosh(0.5) << '\n';
if (errno == EDOM)
std::cout
<< "errno == EDOM: "
<< std::strerror(errno) << '\n';
if (std::fetestexcept(FE_INVALID))
std::cout
<< "FE_INVALID raised\n";
}
acosh(1) = 0
acosh(10) = 2.99322
acosh(DBL_MAX) = 710.476
acosh(Inf) = inf
acosh(0.5) = -nan
errno == EDOM: Numerical argument out of domain
FE_INVALID raised