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std::tanh(std::valarray)

From cppreference.com
< cpp‎ | numeric‎ | valarray
 
 
Numerics library
 
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.

[edit] Parameters

va - value array to apply the operation to

[edit] Return value

Value array containing hyperbolic tangent of the values in va.

[edit] 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:

[edit] 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
}

[edit] 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

[edit] See also

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