Precedence and Associativity

Understanding operator precedence and associativity is crucial in C programming, as it determines the order in which expressions are evaluated. This helps in writing correct and efficient code. Below is a detailed explanation of both concepts.

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1. Operator Precedence

Operator precedence defines the order in which different operators in an expression are evaluated. Operators with higher precedence are evaluated before those with lower precedence. Here’s a general hierarchy of operator precedence in C, from highest to lowest:

• Highest Precedence:
  • Postfix Operators: () (function call), [] (array subscript), -> (structure pointer), . (structure member)
  • Unary Operators: ++ (increment), -- (decrement), + (unary plus), - (unary minus), ! (logical NOT), ~(bitwise NOT), * (dereference), & (address-of), sizeof, type casts (type)
• Intermediate Precedence:
  • Multiplicative Operators: *, /, %
  • Additive Operators: +, -
  • Bitwise Shift Operators: <<, >>
• Relational Operators: <, <=, >, >=
• Equality Operators: ==, !=
• Bitwise AND: &
• Bitwise XOR: ^
• Bitwise OR: |
• Logical AND: &&
• Logical OR: ||
• Conditional Operator: ?:
• Assignment Operators: =, +=, -=, *=, /=, %=, <<=, >>=, &=, ^=, |=
• Comma Operator: , (lowest precedence)

2. Operator Associativity

Associativity defines the order in which operators of the same precedence level are evaluated. Operators can be left-to-right or right-to-left in their evaluation.

• Left-to-Right Associativity:
  • Operators that associate from left to right are evaluated in the order they appear from left to right. Most binary operators, such as arithmetic and bitwise operators, fall into this category.
• Right-to-Left Associativity:
  • Operators that associate from right to left are evaluated in the reverse order. Assignment operators and the conditional (ternary) operator (?:) are examples of this.

3. Detailed Table of Precedence and Associativity

Here’s a comprehensive table summarizing the precedence and associativity of all operators in C:

Precedence Level	Operator	Description	Associativity
1	() [] -> .	Function call, array subscript, structure access	Left-to-right
2	++ -- (postfix)	Postfix increment and decrement	Left-to-right
3	++ -- (prefix), + - ! ~ * &sizeof	Prefix increment/decrement, unary operators, type casts	Right-to-left
4	* / %	Multiplication, division, modulo	Left-to-right
5	+ -	Addition, subtraction	Left-to-right
6	<< >>	Bitwise left shift, right shift	Left-to-right
7	< <= > >=	Relational operators	Left-to-right
8	== !=	Equality operators	Left-to-right
9	&	Bitwise AND	Left-to-right
10	^	Bitwise XOR	Left-to-right
11	`	`	Bitwise OR
12	&&	Logical AND	Left-to-right
13	|	Logical OR	Left-to-right
14	?:	Ternary conditional operator	Right-to-left
15	= += -= *= /= %= >>= <<= &=^= `	Assignment operators	Left-to-right
16	,	Comma operator	Left-to-right