C++ 17中的std :: clamp

将变量钳位到给定范围[高–低]。

If num > high, num is assigned high.
If num < low, num is assigned low.
If num is already clamped, no modifications.

注意：此函数是从C++ 17开始的标头中定义的。

例子：

Input : num = 100, Range : 10 - 90
Output : num = 90

Input : num = 5, Range : 10 - 90
Output : num = 10

Input : num = 50, Range : 10 - 90
Output : num = 50

句法 ：

templateconstexpr const T& clamp( const T& num, const T& low, const T& high );
template
constexpr const T& clamp( const T& v, const T& lo, const T& hi, Compare comp );
Parameters
num      -    the value to clamp
low, high  -    the boundaries to clamp num to
comp      -    comparison function object which returns ?true if low is less than num
                and num is less than high. 

Return value
Reference to low if num is less than low,
Reference to high if high is less than num,
otherwise reference to num.

Applications :
To keep a list of inputs specified to a given range. 
Preventing size overflow.

// CPP program to illustrate
// std::clamp
#include 
  
// Driver code
int main()
{
    // range [10 - 100]
    int high = 100, low = 10;
  
    // num1 higher than range
    int num1 = 120;
  
    // num2 lower than range
    int num2 = 5;
  
    // num3 in range
    int num3 = 50;
  
    // clamping all variables
    num1 = std::clamp(num1, low, high);
    num2 = std::clamp(num2, low, high);
    num3 = std::clamp(num3, low, high);
  
    // printing result
    std::cout << num1 << " " << num2 << " " << num3;
}

输出：

100 10 50

// CPP program to illustrate clamping
// array elements in given range
#include 
#include 
  
// Range [30 - 60]
int low = 30, high = 60;
  
// Function to clamp the elements in given range
void clamp_arr_in_range(int arr[], int n)
{
    // Clamping the array elements
    for (int i = 0; i < n; i++) {
        arr[i] = std::clamp(arr[i], low, high);
    }
}
  
// Driver code
int main()
{
    // Array having elements to be clamped
    int arr[] = { 10, 20, 30, 40, 50, 60, 70, 80 };
  
    // Size of array
    int n = sizeof(arr) / sizeof(arr[0]);
  
    // Function call to clamp the elements
    clamp_arr_in_range(arr, n);
  
    // Printing the array
    for (int i = 0; i < n; i++)
        std::cout << arr[i] << " ";
}

输出 ：

30 30 30 40 50 60 60 60

带二元谓词

// C++ program to implement std::clamp
// with Binary Predicate
  
#include 
  
// Binary predicate
bool comp(int a, int b)
{
    return (a < b);
}
  
// Driver code
int main()
{
    // range [10 - 100]
    int high = 100, low = 10;
  
    // num1 higher than range
    int num1 = 120;
  
    // num2 lower than range
    int num2 = 5;
  
    // num3 in range
    int num3 = 50;
  
    // clamping all variables
    num1 = std::clamp(num1, low, high, comp);
    num2 = std::clamp(num2, low, high, comp);
    num3 = std::clamp(num3, low, high, comp);
  
    // printing result
    std::cout << num1 << " " << num2 << " " << num3;
}

输出：

100 10 50

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