Is (4 > y > 1) a Valid C Expression, and How Is It Evaluated?

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Evaluating Chained Logical Operators in C : Is (4 > y > 1) a Valid Statement?

A common question in C programming arises when evaluating chained logical operators, such as in the expression (4 > y > 1). This article will explore the validity and evaluation of such statements, providing insights into how logical operators operate in C .

Syntax and Parsing

The expression (4 > y > 1) is parsed as ((4 > y) > 1). This means that the comparison operators > are evaluated left-to-right, resulting in a logical value of 0 (false) or 1 (true) for each comparison.

Evaluation

In the given expression, 4 > y will evaluate to 1 if y is less than 4, and 0 if y is greater than or equal to 4. The result of this comparison is then compared to 1 with the second > operator.

Since 0 or 1 is never greater than 1, the entire statement will always return false. However, there is one exception to this rule:

Operator Overloading

If y is an instance of a custom class and the > operator has been overloaded to perform a non-standard comparison, then the behavior of the expression can change. For instance, overloading the > operator to return a mytype object would cause the statement to fail compilation.

Alternative Expression

To make the expression more intuitive, it can be rewritten as:

(4 > y) && (y > 1)

This expression uses the logical AND operator (&&) to combine two separate comparisons, resulting in a true result if both comparisons are true. Unlike the original expression, this rewritten expression provides a clearer understanding of the intended evaluation.

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