Operator Precedence and Associativity in C

What is Operator Associativity in C?

The direction in which an expression is evaluated is determined by the associativity of operators. Associativity is utilized when two operators of the same precedence exist in an expression. Associativity can be either left to right or right to left.

For example, consider x = 5 / 3 * 3; 

Here, the value of x will be assigned as 3 and not 5. ‘*’ operator and ‘/’ operator have the same precedence, but their associativity is from Left to Right. So first 5 is divided by 3 to get 1, and then 1 is multiplied by 3, resulting in 3.

Key Points About Operator Precedence and Associativity in C.

When two or more operators have the same precedence, associativity is utilized.

Example

#include <stdio.h>


int main()
{


    printf("Output of 1 == 2 != 3 is %d",1 == 2 != 3);
    
    return 0;
}

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Output:

Output of 1 == 2 != 3 is 1

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In this case, the operators ‘==’ and ‘!=’ have the same priority. And they are related from left to right. As a result, 1 == 2 is executed first.

Also see, Floyd's Triangle in C

All operators with the same precedence have the same associativity. 

This is required because otherwise, the compiler would be unable to determine the evaluation order of phrases with two operators with the same precedence but differing associativity. For example, the associativity of + and – is the same.

Comma has the least precedence. 

The comma has the least precedence among all operators and should be used with caution.

Example

#include <stdio.h>
int main()
{
    int a;
    a = 10, 20, 30; 
    printf("%d", a);
    return 0;
}

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Output:

10

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Here /the expression is Evaluated as (a = 1), 2, 3.

Postfix Increment and Prefix Increment have different Precedence and Associativity.

Postfix ++ has more precedence than prefix ++, and their associativity is also different. The associativity of postfix ++ is left to right, while that of prefix ++ is right to left.

No comparison chaining of operators in C 

In Python, an expression such as "c > b > a" is handled as "c > b and b > a," while in C, this sort of chaining does not occur.

Example

#include <stdio.h>
int main()
{
    int x = 1, y = 2, z = 3;
    if (x > y > z)
        printf("True");
    else
        printf("False");
    return 0;
}

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Output:

False

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Here (x > y > z) is treated as ((x  > y) > z) because associativity of '>' is from left to right. Therefore the expression becomes ((30 > 20) > 10) which becomes (1 > 10) which results in false condition.

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Operator Precedence and Associativity Table

In this table, operators with the highest precedence appear at the top, while those with the lowest appear at the bottom. Higher precedence operators in an expression will be evaluated first.

Also see : C Static Function and  Short int in C Programming

Frequently Ask Questions

Which of the operators has higher precedence, the addition or subtraction?

In most programming languages, including C, C++, and Python, the operator with the lowest precedence is typically the assignment operator (=).

Which of the operators has higher precedence, multiplication or division?

In programming, multiplication (*) and division (/) operators have the same level of precedence, which is higher than addition and subtraction.

Which operator has the lowest precedence?

Addition (+) and subtraction (-) also share the same precedence level in programming. Their precedence is lower compared to multiplication and division.

Conclusion

In this article, we talked about operator precedence and associativity in C. We learned that precedence determines the order of operator evaluation, while associativity defines the direction of evaluation for operators with equal precedence. With the help of these concepts and by following C's well-defined rules, developers can write accurate expressions and ensure their code behaves as intended. We also discussed which operator has the highest and lowest precedence with proper table of operators.

Recommended Reading:

Difference Between List and Set

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