postdecrement

The postdecrement operator, commonly written as x--, is a postfix unary operator found in many programming languages. It decreases the value of its operand by 1 while returning the operand's original value.

In languages such as C, C++, Java, and JavaScript, the operator is applied as a side effect after the value is produced. The result of the expression is the value before the decrement; the operand is reduced by 1 for subsequent use.

Examples: int i = 5; int a = i--; // a becomes 5, i becomes 4. In an array access, arr[i--] uses the current i as the index, then i is decremented. The postfix form contrasts with the prefix decrement, --i, which decrements first and returns the new value.

Precedence and evaluation: Postfix decrement generally binds tightly in expressions, higher than most binary operators, and is evaluated after the operand's value is obtained but before control proceeds to the next sequence point in languages that distinguish sequencing.

Usage notes and pitfalls: In C/C++, using i-- in the same expression as other reads or writes of i can cause undefined behavior if not properly sequenced. In scripting languages like JavaScript, the operator is well defined for common usages but can produce surprising results in complex expressions.

Other languages: not all languages include a postdecrement operator. Python, for example, does not have i--. Some languages expose similar behavior with function calls or methods rather than operators.

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