C++ 运算符

Operator是用于对变量和值执行操作的符号。例如，+ 是用于加法的运算符，而 - 是用于减法的运算符。

C++ 中的运算符可分为 6 类

1. 算术运算符
2. 赋值运算符
3. 关系运算符
4. 逻辑运算符
5. 位运算符
6. 其他运算符

1. C++ Arithmetic Operators

Arithmetic operators are used to perform arithmetic operations on variables and data. For example,

a + b;

Here, the + operator is used to add two variables a and b. Similarly there are various other arithmetic operators in C++.

示例 1：算术运算符

#include <iostream>
using namespace std;

int main() {
    int a, b;
    a = 7;
    b = 2;

    // printing the sum of a and b
    cout << "a + b = " << (a + b) << endl;

    // printing the difference of a and b
    cout << "a - b = " << (a - b) << endl;

    // printing the product of a and b
    cout << "a * b = " << (a * b) << endl;

    // printing the division of a by b
    cout << "a / b = " << (a / b) << endl;

    // printing the modulo of a by b
    cout << "a % b = " << (a % b) << endl;

    return 0;
}

输出

a + b = 9
a - b = 5
a * b = 14
a / b = 3
a % b = 1

Here, the operators +, - and * compute addition, subtraction, and multiplication respectively as we might have expected.

/ 除法运算符

Note the operation (a / b) in our program. The / operator is the division operator.

As we can see from the above example, if an integer is divided by another integer, we will get the quotient. However, if either divisor or dividend is a floating-point number, we will get the result in decimals.

In C++,

7/2 is 3
7.0 / 2 is 3.5
7 / 2.0 is 3.5
7.0 / 2.0 is 3.5

% 模运算符

The modulo operator % computes the remainder. When a = 9 is divided by b = 4, the remainder is 1.

Note: The % operator can only be used with integers.

自增和自减运算符

C++ also provides increment and decrement operators: ++ and -- respectively.

• ++ increases the value of the operand by 1
• -- decreases it by 1

例如，

int num = 5;

// increment operator
++num;  // 6

Here, the code ++num; increases the value of num by 1.

Example 2: Increment and Decrement Operators

// Working of increment and decrement operators

#include <iostream>
using namespace std;

int main() {
    int a = 10, b = 100, result_a, result_b;

    // incrementing a by 1 and storing the result in result_a
    result_a = ++a;
    cout << "result_a = " << result_a << endl;


    // decrementing b by 1 and storing the result in result_b   
    result_b = --b;
    cout << "result_b = " << result_b << endl;

    return 0;
}

输出

result_a = 11
result_b = 99

In the above program, we have used the ++ and -- operators as prefixes (++a and --b). However, we can also use these operators as postfix (a++ and b--).

To learn more, visit increment and decrement operators.

2. C++ Assignment Operators

In C++, assignment operators are used to assign values to variables. For example,

// assign 5 to a
a = 5;

Here, we have assigned a value of 5 to the variable a.

Example 3: Assignment Operators

#include <iostream>
using namespace std;

int main() {
    int a, b;

    // 2 is assigned to a
    a = 2;

    // 7 is assigned to b
    b = 7;

    cout << "a = " << a << endl;
    cout << "b = " << b << endl;
    cout << "\nAfter a += b;" << endl;

    // assigning the sum of a and b to a
    a += b;  // a = a +b
    cout << "a = " << a << endl;

    return 0;
}

输出

a = 2
b = 7

After a += b;
a = 9

3. C++ Relational Operators

A relational operator is used to check the relationship between two operands. For example,

// checks if a is greater than b
a > b;

Here, > is a relational operator. It checks if a is greater than b or not.

If the relation is true, it returns 1 whereas if the relation is false, it returns 0.

Example 4: Relational Operators

#include <iostream>
using namespace std;

int main() {
    int a, b;
    a = 3;
    b = 5;
    bool result;

    result = (a == b);   // false
    cout << "3 == 5 is " << result << endl;

    result = (a != b);  // true
    cout << "3 != 5 is " << result << endl;

    result = a > b;   // false
    cout << "3 > 5 is " << result << endl;

    result = a < b;   // true
    cout << "3 < 5 is " << result << endl;

    result = a >= b;  // false
    cout << "3 >= 5 is " << result << endl;

    result = a <= b;  // true
    cout << "3 <= 5 is " << result << endl;

    return 0;
}

输出

3 == 5 is 0
3 != 5 is 1
3 > 5 is 0
3 < 5 is 1
3 >= 5 is 0
3 <= 5 is 1

Note: Relational operators are used in decision-making and loops.

4. C++ Logical Operators

Logical operators are used to check whether an expression is true or false. If the expression is true, it returns 1 whereas if the expression is false, it returns 0.

In C++, logical operators are commonly used in decision making. To further understand the logical operators, let's see the following examples,

Suppose,
a = 5
b = 8

Then,

(a > 3) && (b > 5) evaluates to true
(a > 3)  && (b < 5) evaluates to false

(a > 3) || (b > 5) evaluates to true
(a > 3) || (b < 5) evaluates to true
(a < 3) || (b < 5) evaluates to false

!(a < 3) evaluates to true
!(a > 3) evaluates to false

Example 5: Logical Operators

#include <iostream>
using namespace std;

int main() {
    bool result;

    result = (3 != 5) && (3 < 5);     // true
    cout << "(3 != 5) && (3 < 5) is " << result << endl;

    result = (3 == 5) && (3 < 5);    // false
    cout << "(3 == 5) && (3 < 5) is " << result << endl;

    result = (3 == 5) && (3 > 5);    // false
    cout << "(3 == 5) && (3 > 5) is " << result << endl;

    result = (3 != 5) || (3 < 5);    // true
    cout << "(3 != 5) || (3 < 5) is " << result << endl;

    result = (3 != 5) || (3 > 5);    // true
    cout << "(3 != 5) || (3 > 5) is " << result << endl;

    result = (3 == 5) || (3 > 5);    // false
    cout << "(3 == 5) || (3 > 5) is " << result << endl;

    result = !(5 == 2);    // true
    cout << "!(5 == 2) is " << result << endl;

    result = !(5 == 5);    // false
    cout << "!(5 == 5) is " << result << endl;

    return 0;
}

输出

(3 != 5) && (3 < 5) is 1
(3 == 5) && (3 < 5) is 0
(3 == 5) && (3 > 5) is 0
(3 != 5) || (3 < 5) is 1
(3 != 5) || (3 > 5) is 1
(3 == 5) || (3 > 5) is 0
!(5 == 2) is 1
!(5 == 5) is 0

Explanation of logical operator program

• (3 != 5) && (3 < 5) evaluates to 1 because both operands (3 != 5) and (3 < 5) are 1 (true).
• (3 == 5) && (3 < 5) evaluates to 0 because the operand (3 == 5) is 0 (false).
• (3 == 5) && (3 > 5) evaluates to 0 because both operands (3 == 5) and (3 > 5) are 0 (false).
• (3 != 5) || (3 < 5) evaluates to 1 because both operands (3 != 5) and (3 < 5) are 1 (true).
• (3 != 5) || (3 > 5) evaluates to 1 because the operand (3 != 5) is 1 (true).
• (3 == 5) || (3 > 5) evaluates to 0 because both operands (3 == 5) and (3 > 5) are 0 (false).
• !(5 == 2) evaluates to 1 because the operand (5 == 2) is 0 (false).
• !(5 == 5) evaluates to 0 because the operand (5 == 5) is 1 (true).

5. C++ Bitwise Operators

In C++, bitwise operators are used to perform operations on individual bits. They can only be used alongside char and int data types.

To learn more, visit C++ bitwise operators.

6. Other C++ Operators

Here's a list of some other common operators available in C++. We will learn about them in later tutorials.

另请阅读

• C++ Operators Precedence and Associativity