C++ 标准库 <valarray>
C++ 的 <valarray> 库是一个用于数值计算的库,它提供了一种高效的方式来处理数值数组。<valarray> 库中的 valarray 类模板允许程序员对数组进行元素级的数学运算,包括加法、减法、乘法、除法等。此外,它还支持更高级的数学函数,如指数、对数、正弦、余弦等。
valarray 是 C++ 标准库中的一个类模板,用于表示和操作数值数组。它提供了一种方便的方式来执行数组的元素级操作。
语法
valarray 的基本语法如下:
#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;
}
实例
1. 创建和初始化 valarray
实例
#include <iostream>
#include <valarray>
int main() {
std::valarray<double> va(5); // 创建一个包含5个double元素的valarray
va = {1.0, 2.0, 3.0, 4.0, 5.0}; // 初始化valarray
for (auto i : va) {
std::cout << i << " ";
}
std::cout << std::endl;
return 0;
}
#include <valarray>
int main() {
std::valarray<double> va(5); // 创建一个包含5个double元素的valarray
va = {1.0, 2.0, 3.0, 4.0, 5.0}; // 初始化valarray
for (auto i : va) {
std::cout << i << " ";
}
std::cout << std::endl;
return 0;
}
输出结果:
1 2 3 4 5
2. 基本运算
实例
#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; // 加法
std::valarray<double> diff = va1 - va2; // 减法
std::valarray<double> prod = va1 * va2; // 乘法
std::valarray<double> quot = va1 / va2; // 除法
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;
}
#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; // 加法
std::valarray<double> diff = va1 - va2; // 减法
std::valarray<double> prod = va1 * va2; // 乘法
std::valarray<double> quot = va1 / va2; // 除法
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;
}
输出结果:
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. 使用 valarray 进行数学函数操作
实例
#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; // 平方
std::valarray<double> roots = std::sqrt(va); // 开方
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;
}
#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; // 平方
std::valarray<double> roots = std::sqrt(va); // 开方
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;
}
输出结果:
Squares: 1 4 9 16 25 Square Roots: 1 1.4142136 1.7320508