C++ 98引入了一个名为valarray的特殊容器，可以有效地保存并提供对数组的数学运算。
- 它支持按元素进行数学运算以及各种形式的广义下标运算符，切片和间接访问。
- 与向量相比，valarray在某些数学运算中比向量更有效。
valarray类中的公共成员函数：
1. apply() ：-该函数将其参数中给出的操作应用于所有valarray元素，并返回具有操作值的新valarray 。
2. sum() ：-此函数返回valarrays的所有元素的总和。
// C++ code to demonstrate the working of
// apply() and sum()
#include
#include // for valarray functions
using namespace std;
int main()
{
// Initializing valarray
valarray varr = { 10, 2, 20, 1, 30 };
// Declaring new valarray
valarray varr1 ;
// Using apply() to increment all elements by 5
varr1 = varr.apply([](int x){return x=x+5;});
// Displaying new elements value
cout << "The new valarray with manipulated values is : ";
for (int &x: varr1) cout << x << " ";
cout << endl;
// Displaying sum of both old and new valarray
cout << "The sum of old valarray is : ";
cout << varr.sum() << endl;
cout << "The sum of new valarray is : ";
cout << varr1.sum() << endl;
return 0;
}
输出：
The new valarray with manipulated values is : 15 7 25 6 35
The sum of old valarray is : 63
The sum of new valarray is : 88
3. min() ：-此函数返回valarray的最小元素。
4. max() ：-此函数返回valarray的最大元素。
// C++ code to demonstrate the working of
// max() and min()
#include
#include // for valarray functions
using namespace std;
int main()
{
// Initializing valarray
valarray varr = { 10, 2, 20, 1, 30 };
// Displaying largest element of valarray
cout << "The largest element of valarray is : ";
cout << varr.max() << endl;
// Displaying smallest element of valarray
cout << "The smallest element of valarray is : ";
cout << varr.min() << endl;
return 0;
}
输出：
The largest element of valarray is : 30
The smallest element of valarray is : 1
5.移()： -该函数返回由在其参数提到的数目的切换元件后的新的valarray。如果数字为正，则应用左移；如果数字为负，则应用右移。
6.环状移位()： -后循环移位(旋转)该函数返回新的valarray通过在其参数提到的数量的元件。如果数字为正，则应用左圆周移位；如果数字为负，则应用右圆周移位。
// C++ code to demonstrate the working of
// shift() and cshift()
#include
#include // for valarray functions
using namespace std;
int main()
{
// Initializing valarray
valarray varr = { 10, 2, 20, 1, 30 };
// Declaring new valarray
valarray varr1;
// using shift() to shift elements to left
// shifts valarray by 2 position
varr1 = varr.shift(2);
// Displaying elements of valarray after shifting
cout << "The new valarray after shifting is : ";
for ( int&x : varr1) cout << x << " ";
cout << endl;
// using cshift() to circulary shift elements to right
// rotates valarray by 3 position
varr1 = varr.cshift(-3);
// Displaying elements of valarray after circular shifting
cout << "The new valarray after circular shifting is : ";
for ( int&x : varr1) cout << x << " ";
cout << endl;
return 0;
}
输出：
The new valarray after shifting is : 20 1 30 0 0
The new valarray after circular shifting is : 20 1 30 10 2
7. swap() ：-此函数一个valarray与另一个valarray交换。
// C++ code to demonstrate the working of
// swap()
#include
#include // for valarray functions
using namespace std;
int main()
{
// Initializing 1st valarray
valarray varr1 = {1, 2, 3, 4};
// Initializing 2nd valarray
valarray varr2 = {2, 4, 6, 8};
// Displaying valarrays before swapping
cout << "The contents of 1st valarray "
"before swapping are : ";
for (int &x : varr1)
cout << x << " ";
cout << endl;
cout << "The contents of 2nd valarray "
"before swapping are : ";
for (int &x : varr2)
cout << x << " ";
cout << endl;
// Use of swap() to swap the valarrays
varr1.swap(varr2);
// Displaying valarrays after swapping
cout << "The contents of 1st valarray "
"after swapping are : ";
for (int &x : varr1)
cout << x << " ";
cout << endl;
cout << "The contents of 2nd valarray "
"after swapping are : ";
for (int &x : varr2)
cout << x << " ";
cout << endl;
return 0;
}
输出：
The contents of 1st valarray before swapping are : 1 2 3 4
The contents of 2nd valarray before swapping are : 2 4 6 8
The contents of 1st valarray after swapping are : 2 4 6 8
The contents of 2nd valarray after swapping are : 1 2 3 4
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