std::tanh(std::valarray)(3)

🌸 std::tanh(std::valarray)(3) 🌸

okay so bestie, this is the std::tanh(std::valarray)(3) page from the C++ Standard Libary manual — yes, “Libary” is literally how the manual name shows up, and we’re keeping it because facts don’t change, only vibes do 💅. This whole page is about applying hyperbolic tangent to every element of a valarray, and it’s giving very “math but make it containerized” energy ✨

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✨ NAME ✨

std::tanh(std::valarray) — std::tanh(std::valarray), that’s the whole name section, bestie. It’s the std::tanh overload for std::valarray, and it is exactly what it says on the tin 🫶

🌈 Synopsis 🌈

Defined in header <valarray>:

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

For each element in va, this computes the hyperbolic tangent of the value of the element. literally element-by-element glow-up 😌

🫶 Parameters 🫶

• va — value array to apply the operation to. that’s the input array, bestie; it’s a const valarray<T>&.

🎀 Return value 🎀

Value array containing hyperbolic tangent of the values in va. so you get a whole value-array vibe back, full of tanh’d values ✨

💅 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 🧚

here’s one way it could look under the hood, no cap:

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, tanhl — computes hyperbolic tangent (\({\small\tanh{x}}\)tanh(x)) (function) (C++11) (C++11)
• tanh(std::complex) — computes hyperbolic tangent of a complex number (\({\small\tanh{z}}\)tanh(z)) (function template)

🙈 Hidden category 🙈

• Pages with unreviewed LWG DR marker

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okay that’s the whole page, bestie. it came from http://cppreference.com, version/date 2024.06.10, and the page name is std::tanh(std::valarray)(3). mwah 💋 stay hyperbolic ✨