Difference between Operator Precedence and Operator Associativity

In programming, operators are used to perform various operations on data. Understanding how operators interact with each other is crucial for writing correct and efficient code. In this article, we will explore the two most important concepts which are Operator Precedence and Operator Associativity.

Operator Precedence:

Operator precedence determines which operation is performed first in an expression with more than one operator with different precedence. Operators with higher precedence are evaluated before those with lower precedence.

Example of Operator Precedence:

Let’s try to evaluate the following expression,

10 + 20 * 30

The expression contains two operators, + (plus), and * (multiply).The multiplication operator * has higher precedence than + so, the first evaluation will be

10 + (20 * 30)

After evaluating the higher precedence operator, the expression is

10 + 600

Now, the + operator will be evaluated.

610

Operator Associativity:

Operator associativity defines the direction in which operators of the same precedence are evaluated when they appear in an expression. It can be either left-to-right or right-to-left.

Example of Operator Associativity:

Let’s evaluate the following expression,

100 / 5 % 2

Both / (division) and % (Modulus) operators have the same precedence, so the order of evaluation will be decided by associativity.

The associativity of the multiplicative operators is from Left to Right. So,

(100 / 5) % 2

After evaluation, the expression will be

20 % 2

Now, the % operator will be evaluated.

0

Operator Precedence and Associativity Table:

The following tables list the operator precedence from highest to lowest and the associativity for each of the operators:

Precedence	Operator	Description	Associativity
1	()	Parentheses (function call)	Left-to-Right
	[]	Array Subscript (Square Brackets)
	.	Dot Operator
	->	Structure Pointer Operator
	++ , —	Postfix increment, decrement
2	++ / —	Prefix increment, decrement	Right-to-Left
	+ / –	Unary plus, minus
	! , ~	Logical NOT,  Bitwise complement
	(type)	Cast Operator
	*	Dereference Operator
	&	Addressof Operator
	sizeof	Determine size in bytes
3	*,/,%	Multiplication, division, modulus	Left-to-Right
4	+/-	Addition, subtraction	Left-to-Right
5	<< , >>	Bitwise shift left, Bitwise shift right	Left-to-Right
6	< , <=	Relational less than, less than or equal to	Left-to-Right
	> , >=	Relational greater than, greater than or equal to
7	== , !=	Relational is equal to, is not equal to	Left-to-Right
8	&	Bitwise AND	Left-to-Right
9	^	Bitwise exclusive OR	Left-to-Right
10	|	Bitwise inclusive OR	Left-to-Right
11	&&	Logical AND	Left-to-Right
12	||	Logical OR	Left-to-Right
13	?:	Ternary conditional	Right-to-Left
14	=	Assignment	Right-to-Left
	+= , -=	Addition, subtraction assignment
	*= , /=	Multiplication, division assignment
	%= , &=	Modulus, bitwise AND assignment
	^= , |=	Bitwise exclusive, inclusive OR assignment
	<<=, >>=	Bitwise shift left, right assignment
15	,	comma (expression separator)	Left-to-Right

Difference between Operator Precedence and Operator Associativity:

Aspect	Operator Precedence	Operator Associativity
Definition	Determines the order of evaluation of operators in an expression.	Defines the direction of evaluation when operators of the same precedence appear.
Priority	Higher precedence operators are evaluated before lower precedence operators.	Associativity determines the order in which operators are evaluated within an expression of the same precedence.
Example	In 2 + 3 * 4, * has higher precedence than +, so 3 * 4 is evaluated first.	In 2 + 3 + 4, left-associative operators are evaluated from left to right.
Representation	Precedence levels are often specified in language documentation or expressed with parentheses in expressions.	Associativity is usually implicit and is determined by the language specification.