std::tanh(std::valarray) - cppreference.com (original) (raw)

| | | | | ---------------------------------------------------------------- | | | | template< class T >valarray<T> tanh( const valarray<T>& va ); | | |

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

Contents

• 1 Parameters
• 2 Return value
• 3 Notes
• 4 Possible implementation
• 5 Example
• 6 See also

[edit] Parameters

[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:

• 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.

[edit] Possible implementation

template valarray tanh(const valarray& va) { valarray other = va; for (T& i : other) i = tanh(i);   return other; // proxy object may be returned }

[edit] Example

#include #include #include   auto show = [](char const* title, const std::valarray& va) { std::cout << title << " :"; for (auto x : va) std::cout << " " << std::fixed << x; std::cout << '\n'; };   int main() { const std::valarray x = {.0, .1, .2, .3}; const std::valarray sinh = std::sinh(x); const std::valarray cosh = std::cosh(x); const std::valarray tanh = std::tanh(x); const std::valarray tanh_by_def = sinh / cosh; const std::valarray tanh_2x = std::tanh(2.0 * x); const std::valarray 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(2x) ", tanh_2x); show("tanh(2x) (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(2x)  : 0.000000 0.197375 0.379949 0.537050 tanh(2x) (def) : 0.000000 0.197375 0.379949 0.537050

[edit] See also