std::exp(std::valarray)(3)

🌈 std::exp(std::valarray) 🌈

okay so bestie, welcome to the std::exp(std::valarray) page from the C++ Standard Libary (section 3) 💅✨ no cap, this one is a tiny math baddie: it applies exp to every element of a valarray and returns a whole new value array.

🌸 NAME 🌸

std::exp(std::valarray) - std::exp(std::valarray) (yes, the name is literally the name twice; it's giving full-name energy 🎀)

✨ Synopsis ✨

Defined in header <valarray>

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

For each element in va, it computes e raised to the power equal to the value of the element. math girlie behavior fr fr 💖

🎀 Parameters 🎀

• va — value array to apply the operation to.

🦋 Return value 🦋

Value array containing e raised by the values in va. 🫶

💜 Notes 💜

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

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 the possible implementation, exactly as the page shows it:

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

    return other; // proxy object may be returned
}

🍓 Example 🍓

This example demonstrates the Euler's identity e^(iπ) = -1 and the related exponents. iconic math moment 🌈

// Run this code

#include <complex>
#include <iostream>
#include <numbers>
#include <valarray>

int main()
{
    const double pi = std::numbers::pi;
    std::valarray<std::complex<double>> v =
    {
        {0, 0}, {0, pi / 2}, {0, pi}, {0, 3 * pi / 2}, {0, 2 * pi}
    };
    std::valarray<std::complex<double>> v2 = std::exp(v);
    for (std::cout << std::showpos << std::fixed; auto n : v2)
        std::cout << n << '\n';
}

💅 Output: 💅

(+1.000000,+0.000000)
(+0.000000,+1.000000)
(-1.000000,+0.000000)
(-0.000000,-1.000000)
(+1.000000,-0.000000)

🌈 See also 🌈

• log(std::valarray) applies the function std::log to each element of valarray (function template)
• exp
• expf returns e raised to the given power (\({\small e^x}\)e^x)
• expl (function)
• (C++11)
• (C++11)
• exp(std::complex) complex base e exponential (function template)

🙈 Hidden category: 🙈

• Pages with unreviewed LWG DR marker

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made with 💖 from http://cppreference.com — version/date 2024.06.10 — page std::exp(std::valarray)(3) 🫶✨