C中的运算符|集合2(关系和逻辑运算符)

我们已经讨论了《 C语言中的运算符简介》，在此我们对什么类型的运算符，C和C++支持及其基本实现有了一个整体的了解。之后，我们研究了算术运算符，从而对C和C++中的算术运算运算符的类型和用法有了详细的了解。在本文中，让我们尝试了解关系运算符和逻辑运算符的类型和用法。

关系运算符
关系运算符用于比较两个值，以了解一对数字份额的关系类型。例如，小于，大于，等于等。让我们一一看一下

1. 等于运算符：表示为‘==’ ，等于运算符检查两个给定的操作数是否相等。如果是这样，则返回true。否则，它返回false。例如， 5 == 5将返回true。
2. 不等于运算符：用‘！=’表示，不等于运算符检查两个给定的操作数是否相等。如果不是，则返回true。否则，它返回false。它是‘==’运算符的精确布尔补码。例如， 5！= 5将返回false。
3. 大于运算符：表示为“>” ，大于运算符检查第一个操作数是否大于第二个操作数。如果是这样，则返回true。否则，它返回false。例如， 6> 5将返回true。
4. 小于运算符：表示为“ <” ，小于运算符检查第一个操作数是否小于第二个操作数。如果是这样，则返回true。否则，它返回false。例如， 6 <5将返回false。
5. 大于或等于运算符：表示为‘> =’ ，大于或等于运算符检查第一个操作数是否大于或等于第二个操作数。如果是这样，则返回true，否则返回false。例如， 5> = 5将返回true。
6. 小于或等于运算符：表示为‘<=’ ，小于或等于运算符检查第一个操作数是否小于或等于第二个操作数。如果是这样，则返回true，否则返回false。例如， 5 <= 5也将返回true。

例子：

C

// C program to demonstrate working of relational operators
#include 
  
int main()
{
    int a = 10, b = 4;
  
    // greater than example
    if (a > b)
        printf("a is greater than b\n");
    else
        printf("a is less than or equal to b\n");
  
    // greater than equal to
    if (a >= b)
        printf("a is greater than or equal to b\n");
    else
        printf("a is lesser than b\n");
  
    // less than example
    if (a < b)
        printf("a is less than b\n");
    else
        printf("a is greater than or equal to b\n");
  
    // lesser than equal to
    if (a <= b)
        printf("a is lesser than or equal to b\n");
    else
        printf("a is greater than b\n");
  
    // equal to
    if (a == b)
        printf("a is equal to b\n");
    else
        printf("a and b are not equal\n");
  
    // not equal to
    if (a != b)
        printf("a is not equal to b\n");
    else
        printf("a is equal b\n");
  
    return 0;
}

C++

// C++ program to demonstrate working of logical operators
#include 
using namespace std;
  
int main()
{
    int a = 10, b = 4;
  
    // greater than example
    if (a > b)
        cout << "a is greater than b\n";
    else
        cout << "a is less than or equal to b\n";
  
    // greater than equal to
    if (a >= b)
        cout << "a is greater than or equal to b\n";
    else
        cout << "a is lesser than b\n";
  
    // less than example
    if (a < b)
        cout << "a is less than b\n";
    else
        cout << "a is greater than or equal to b\n";
  
    // lesser than equal to
    if (a <= b)
        cout << "a is lesser than or equal to b\n";
    else
        cout << "a is greater than b\n";
  
    // equal to
    if (a == b)
        cout << "a is equal to b\n";
    else
        cout << "a and b are not equal\n";
  
    // not equal to
    if (a != b)
        cout << "a is not equal to b\n";
    else
        cout << "a is equal b\n";
  
    return 0;
}

输出：

a is greater than b
a is greater than or equal to b
a is greater than or equal to b
a is greater than b
a and b are not equal
a is not equal to b

逻辑运算符：
它们用于组合两个或多个条件/约束或补充对所考虑的原始条件的评估。如下所述：

1. 逻辑AND运算符：当同时考虑两个条件时， “ &&”运算符返回true。否则，它返回false。例如，当a和b都为真(即非零)时， && b返回真。
2. 逻辑OR运算符： “ ||”即使满足所考虑条件中的一个(或两个)，运算符将返回true。否则，它返回false。例如， ||如果a或b之一或两者均为true(即非零)，则b返回true。当然，当a和b都为true时，它将返回true。
3. 逻辑非运算符： “！”运算符返回true，即不满足考虑条件。否则，它返回false。例如，如果a为假，即a = 0时， ！a返回true。

例子：

C

// C program to demonstrate working of logical operators
#include 
  
int main()
{
    int a = 10, b = 4, c = 10, d = 20;
  
    // logical operators
  
    // logical AND example
    if (a > b && c == d)
        printf("a is greater than b AND c is equal to d\n");
    else
        printf("AND condition not satisfied\n");
  
    // logical AND example
    if (a > b || c == d)
        printf("a is greater than b OR c is equal to d\n");
    else
        printf("Neither a is greater than b nor c is equal "
               " to d\n");
  
    // logical NOT example
    if (!a)
        printf("a is zero\n");
    else
        printf("a is not zero");
  
    return 0;
}

C++

// C++ program to demonstrate working of
// logical operators
#include 
using namespace std;
  
int main()
{
    int a = 10, b = 4, c = 10, d = 20;
  
    // logical operators
  
    // logical AND example
    if (a > b && c == d)
        cout << "a is greater than b AND c is equal to d\n";
    else
        cout << "AND condition not satisfied\n";
  
    // logical AND example
    if (a > b || c == d)
        cout << "a is greater than b OR c is equal to d\n";
    else
        cout << "Neither a is greater than b nor c is equal "
                " to d\n";
  
    // logical NOT example
    if (!a)
        cout << "a is zero\n";
    else
        cout << "a is not zero";
  
    return 0;
}

输出：

AND condition not satisfied
a is greater than b OR c is equal to d
a is not zero

逻辑运算符中的短路：

• 在逻辑AND的情况下，如果第一个操作数为false，则不评估第二个操作数。例如，下面的程序1不打印“ GeeksQuiz”，因为逻辑AND的第一个操作数本身为false。

  C

  #include 
  #include 
  int main()
  {
      int a = 10, b = 4;
      bool res = ((a == b) && printf("GeeksQuiz"));
      return 0;
  }
  

  C++

  #include 
  using namespace std;
    
  int main()
  {
      int a = 10, b = 4;
      bool res = ((a == b) && cout << "GeeksQuiz");
      return 0;
  }
  

  输出：

  No Output
  

  但是下面的程序将“ GeeksQuiz”打印为逻辑AND的第一个操作数为true。

  C

  #include 
  #include 
  int main()
  {
      int a = 10, b = 4;
      bool res = ((a != b) && printf("GeeksQuiz"));
      return 0;
  }
  

  C++

  #include 
  using namespace std;
    
  int main()
  {
      int a = 10, b = 4;
      bool res = ((a != b) && cout << "GeeksQuiz");
      return 0;
  }
  

  输出：

  GeeksQuiz
  

• 在逻辑OR的情况下，如果第一个操作数为true，则不评估第二个操作数。例如，下面的程序1不打印“ GeeksQuiz”，因为逻辑OR的第一个操作数本身为true。

  C

  #include 
  #include 
  int main()
  {
      int a = 10, b = 4;
      bool res = ((a != b) || printf("GeeksQuiz"));
      return 0;
  }
  

  C++

  #include 
  #include 
  int main()
  {
      int a = 10, b = 4;
      bool res = ((a != b) || cout << "GeeksQuiz");
      return 0;
  }
  

  输出：

  No Output
  

  但是下面的程序将打印“ GeeksQuiz”，因为逻辑OR的第一个操作数为false。

  C

  #include 
  #include 
  int main()
  {
      int a = 10, b = 4;
      bool res = ((a == b) || printf("GeeksQuiz"));
      return 0;
  }
  

  C++

  #include 
  #include 
  int main()
  {
      int a = 10, b = 4;
      bool res = ((a == b) || cout << "GeeksQuiz");
      return 0;
  }
  

  输出：

  GeeksQuiz
  

C语言中的操作员测验

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