C++ Standard Library<valarray>

C++'s<valarray>The library is a library for numerical computation, providing an efficient way to handle numerical arrays.<valarray>In the libraryvalarrayThe class template allows programmers to perform element-wise mathematical operations on arrays, including addition, subtraction, multiplication, division, etc. In addition, it also supports more advanced mathematical functions such as exponential, logarithmic, sine, cosine, etc.

valarrayIt is a class template in the C++ standard library used to represent and manipulate numerical arrays. It provides a convenient way to perform element-wise operations on arrays.

Syntax

valarrayThe basic syntax is as follows:

#include <valarray>

int main() {
    std::valarray<double> va(10); // 创建一个包含10个double元素的valarray
    va = 1; // 将所有元素初始化为1
    // ...
    return 0;
}

Example

1. Create and initialize valarray

Example

#include <iostream>
#include <valarray>

int main() {
    std::valarray<double> va(5); // Create a valarray containing 5 double elements
    va = {1.0, 2.0, 3.0, 4.0, 5.0}; // Initialize valarray

    for (auto i : va) {
        std::cout << i << " ";
    }
    std::cout << std::endl;

    return 0;
}

Output:

1 2 3 4 5

2. Basic Operations

Example

#include <iostream>
#include <valarray>

int main() {
    std::valarray<double> va1(5), va2(5);
    va1 = {1.0, 2.0, 3.0, 4.0, 5.0};
    va2 = {2.0, 3.0, 4.0, 5.0, 6.0};

    std::valarray<double> sum = va1 + va2; // Addition
    std::valarray<double> diff = va1 - va2; // Subtraction
    std::valarray<double> prod = va1 * va2; // Multiplication
    std::valarray<double> quot = va1 / va2; // Division

    std::cout << "Sum: ";
    for (auto i : sum) {
        std::cout << i << " ";
    }
    std::cout << std::endl;

    std::cout << "Difference: ";
    for (auto i : diff) {
        std::cout << i << " ";
    }
    std::cout << std::endl;

    std::cout << "Product: ";
    for (auto i : prod) {
        std::cout << i << " ";
    }
    std::cout << std::endl;

    std::cout << "Quotient: ";
    for (auto i : quot) {
        std::cout << i << " ";
    }
    std::cout << std::endl;

    return 0;
}

Output:

Sum: 3 5 7 9 11 
Difference: -1 -1 1 1 -1 
Product: 2 6 12 20 30 
Quotient: 0.5 0.6666667 0.75 0.8 0.8333334

3. Using valarray for mathematical function operations

Example

#include <iostream>
#include <valarray>
#include <cmath>

int main() {
    std::valarray<double> va(5);
    va = {1.0, 2.0, 3.0, 4.0, 5.0};

    std::valarray<double> squares = va * va; // Square
    std::valarray<double> roots = std::sqrt(va); // Square root

    std::cout << "Squares: ";
    for (auto i : squares) {
        std::cout << i << " ";
    }
    std::cout << std::endl;

    std::cout << "Square Roots: ";
    for (auto i : roots) {
        std::cout << i << " ";
    }
    std::cout << std::endl;

    return 0;
}

Output:

Squares: 1 4 9 16 25 
Square Roots: 1 1.4142136 1.7320508
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