expressionstatement

An expressionstatement is a type of programming language statement that consists of a single expression, evaluated for its side effects. In many languages, the value produced by the expression is not used by the surrounding code and is typically discarded after evaluation. The concept is common in languages such as C, C++, Java, and JavaScript, though exact syntax and terminology can vary.

In practice, expression statements are used to perform operations that change program state or have observable effects, such as assignments, function or method calls, and increment or decrement operations. For example, in C or C++, statements like i = 5;, foo(bar()); and i++; are all expression statements. The semicolon or the language’s statement terminator marks the end of the statement.

The formal grammar of an expression statement generally restricts the statement to a single expression followed by the statement terminator. The expression itself may have side effects, and these effects occur whether or not the value of the expression is subsequently used. If the expression would yield a value, that value is typically ignored when the statement is executed.

In compilers and language implementations, expression statements are represented as distinct nodes or constructs in the abstract syntax tree. They are grouped with other statements as part of a program’s control flow, separate from declarations or block constructs.

While expression statements are widely supported, some languages offer other constructs that resemble expressions but differ in how their results are used. Developers should be mindful of unused results and potential side effects when writing expression statements, as they can affect readability and maintainability.