NAME¶

std::tanh(std::valarray) - std::tanh(std::valarray)

Synopsis¶

Defined in header <valarray>
template< class T >
valarray<T> tanh( const valarray<T>& va );

For each element in va computes hyperbolic tangent of the value of the element.

Parameters¶

va - value array to apply the operation to

Return value¶

Value array containing hyperbolic tangent of the values in va.

Notes¶

Unqualified function (tanh) is used to perform the computation. If such function is
not available, std::tanh is used due to argument-dependent lookup.

The function can be implemented with the return type different from std::valarray.
In this case, the replacement type has the following properties:

* All const member functions of std::valarray are provided.
* std::valarray, std::slice_array, std::gslice_array, std::mask_array and
std::indirect_array can be constructed from the replacement type.
* For every function taking a const std::valarray<T>&
except begin() and end()
(since C++11), identical functions taking the replacement types shall be added;
* For every function taking two const std::valarray<T>& arguments, identical
functions taking every combination of const std::valarray<T>& and replacement
types shall be added.
* The return type does not add more than two levels of template nesting over the
most deeply-nested argument type.

Possible implementation¶

template<class T>
valarray<T> tanh(const valarray<T>& va)
{
valarray<T> other = va;
for (T& i : other)
i = tanh(i);

return other; // proxy object may be returned
}

Example¶

// Run this code

#include <cmath>
#include <iostream>
#include <valarray>

auto show = [](char const* title, const std::valarray<double>& va)
{
std::cout << title << " :";
for (auto x : va)
std::cout << " " << std::fixed << x;
std::cout << '\n';
};

int main()
{
const std::valarray<double> x = {.0, .1, .2, .3};
const std::valarray<double> sinh = std::sinh(x);
const std::valarray<double> cosh = std::cosh(x);
const std::valarray<double> tanh = std::tanh(x);
const std::valarray<double> tanh_by_def = sinh / cosh;
const std::valarray<double> tanh_2x = std::tanh(2.0 * x);
const std::valarray<double> tanh_2x_by_def =
(2.0 * tanh) / (1.0 + std::pow(tanh, 2.0));

show("x ", x);
show("tanh(x) ", tanh);
show("tanh(x) (def) ", tanh_by_def);
show("tanh(2*x) ", tanh_2x);
show("tanh(2*x) (def)", tanh_2x_by_def);
}

Output:¶

x : 0.000000 0.100000 0.200000 0.300000
tanh(x) : 0.000000 0.099668 0.197375 0.291313
tanh(x) (def) : 0.000000 0.099668 0.197375 0.291313
tanh(2*x) : 0.000000 0.197375 0.379949 0.537050
tanh(2*x) (def) : 0.000000 0.197375 0.379949 0.537050

See also¶

sinh(std::valarray) applies the function std::sinh to each element of valarray
(function template)
cosh(std::valarray) applies the function std::cosh to each element of valarray
(function template)
tanh
tanhf computes hyperbolic tangent (\({\small\tanh{x}}\)tanh(x))
tanhl (function)
(C++11)
(C++11)
computes hyperbolic tangent of a complex number
tanh(std::complex) (\({\small\tanh{z}}\)tanh(z))
(function template)

Hidden category:¶

* Pages with unreviewed LWG DR marker