C / C++中的islessequal()

在C++中，islessequal()是math.h中的预定义函数。用于检查第一个浮点数是否小于或等于第二个浮点。与简单比较相比，它提供的优势是，它在进行比较时不会引发浮点异常。例如，如果两个参数之一是NaN，则它返回false而不引发异常。

句法：

bool isgreaterequal(a, b)

Parameters:

• a, b => These two are the parameters whose value we want to compare.

Result:

• The function will return the true if a <= b else it returns false.

Error:

No error occurs with this function.

Exception:

• If a or b or both is NaN then the function raised an exception and return false(0).

对此的说明如下

// CPP code to illustrate
// the exception of function
#include 
using namespace std;
  
int main()
{
    // Take any values
    float a = 5.5;
    double f1 = nan("1");
    bool result;
  
    // Since f1 value is NaN so
    // with any value of a, the function
    // always return false(0)
    result = islessequal(a, f1);
    cout << a << " islessequal " << f1
         << ": " << result;
  
    return 0;
}

输出：

5.5 islessequal nan: 0

例子：

• 程序1：

  // CPP code to illustrate
  // the use of islessequal function
  #include 
  using namespace std;
    
  int main()
  {
      // Take two any values
      float a, b;
      bool result;
      a = 5.2;
      b = 8.5;
    
      // Since 'a' is less than
      // equal to 'b' so answer
      // is true(1)
      result = islessequal(a, b);
      cout << a << " islessequal to " << b
           << ": " << result << endl;
    
      int x = 8;
      int y = 5;
    
      // Since 'x' is not less
      // than equal to 'y' so answer
      // is false(0)
      result = islessequal(x, y);
      cout << x << " islessequal to " << y
           << ": " << result;
    
      return 0;
  }
  

  注意：使用此函数，您还可以将任何数据类型与任何其他数据类型进行比较。

• 程式2：

  // CPP code to illustrate
  // the use of islessequal function
  #include 
  using namespace std;
    
  int main()
  {
      // Take any two values
      bool result;
      float a = 80.23;
      int b = 82;
    
      // Since 'a' is less
      // than equal to 'b' so answer
      // is true(1)
      result = islessequal(a, b);
      cout << a << " islessequal to " << b
           << ": " << result << endl;
    
      char x = 'c';
    
      // Since 'c' ascii value(99) is not
      // less than variable a so answer
      // is false(0)
      result = islessequal(x, a);
      cout << x << " islessequal to " << a
           << ": " << result;
    
      return 0;
  }
  

  输出：

  80.23 islessequal to 82: 1
  c islessequal to 80.23: 0
  

应用范围：
在许多应用程序中，我们可以使用islessequal()函数比较两个值，例如在while循环中使用它来打印前10个自然数。

// CPP code to illustrate
// the use of islessequal function
#include 
using namespace std;
  
int main()
{
    int i = 1;
    while (islessequal(i, 10)) {
        cout << i << " ";
        i++;
    }
    return 0;
}

输出：

1 2 3 4 5 6 7 8 9 10 

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