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std::tanh(std::valarray)

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:

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

#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

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

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