Statements and Operators: Operator Precedence

What is it?

Operator precedence in C++ is a set of rules that dictate the order in which operations are performed in expressions that contain more than one operator. C++ operators have different levels of precedence. Operators with higher precedence are performed first, and operators of equal precedence are performed from left to right.


Operator Precedence Chart

The C++ operators are arranged here in decreasing order of precedence:

Precedence Operator Description
1 :: Scope resolution
2 a++, a--, typeid, const_cast, dynamic_cast, reinterpret_cast, static_cast Postfix increment and decrement, typeid operator, type cast operators
3 ++a, --a, +a, -a, !, ~, (type), *a, &a, sizeof Prefix increment and decrement, unary plus and minus, logical NOT, bitwise NOT, C-style cast, dereference, address-of, sizeof
4 .*, ->* Pointer to member
5 *, /, % Multiplication, division, modulo
6 +, - Addition, subtraction
7 <<, >> Bitwise shift left, bitwise shift right
8 <, <=, >, >= Less than, less than or equal, greater than, greater than or equal
9 ==, != Equality, inequality
10 & Bitwise AND
11 ^ Bitwise XOR
12 ` `
13 && Logical AND
14 `
15 ?: Ternary conditional
16 =, +=, -=, *=, /=, %=, &=, ` =, ^=, <<=, >>=`
17 , Comma



C++ Statements and Operators: operator precedence



How to use it

The following steps explain how you can use C++ operator precedence in your code:

  1. Write an expression containing multiple operators.
  2. Understand the precedence levels of these operators based on the operator precedence chart.
  3. The operations will be performed according to the precedence levels of the operators. If parentheses () are used, operations within the parentheses will be performed first.



Program code snippet example

#include <iostream>

using namespace std;

int main() {
    int a = 2, b = 3, c = 4, d = 5;
    int result = a + b * c / d; // Here, multiplication and division have higher precedence than addition.
    cout << "Result: " << result << endl;

    result = (a + b) * c / d; // Parentheses have the highest precedence, so a + b will be calculated first.
    cout << "Result: " << result << endl;

    return 0;
}

Output:

Result: 4
Result: 5



Important to know

  • Operator precedence helps in deciding the grouping of terms in an expression. This allows the expression to be evaluated correctly.
  • The parentheses () can be used to alter the precedence order. The operations within the parentheses are performed first regardless of operator precedence.
  • When operators

have the same level of precedence, they are processed according to their associativity, usually from left to right.



Best practices

  1. Use parentheses: Although C++ has defined operator precedence rules, using parentheses to make the order of operations explicit can make the code easier to read and understand. This can also help avoid errors.

  2. Understand operator precedence: Make sure to understand and remember the operator precedence rules to correctly write and interpret complex expressions.

  3. Avoid relying on implicit order of operations: Relying on the implicit order of operations can make the code harder to read and debug. It's better to make the order of operations explicit using parentheses.



Calculate each expression of a, b, and c so a equals 65, b equals 15 and c equals 8.