isExpr

isExpr is a function commonly found in programming language parsers and Abstract Syntax Tree (AST) manipulation libraries. Its primary purpose is to determine if a given node or token represents an expression. An expression is a piece of code that evaluates to a value. This contrasts with statements, which perform an action.

The `isExpr` function typically takes a node or token as input and returns a boolean value: true if it's an expression, and false otherwise. The specific criteria for what constitutes an expression can vary depending on the programming language and the parser's implementation. However, common examples of expressions include literals (like numbers or strings), variable references, function calls, arithmetic operations (e.g., `a + b`), and comparisons (e.g., `x > 5`).

In practice, `isExpr` is crucial for tasks such as syntax validation, code analysis, and transformation. For instance, a compiler might use `isExpr` to ensure that an operand in an operation is indeed an expression that can yield a value. Similarly, code linters or refactoring tools might employ `isExpr` to identify specific types of code constructs for analysis or modification. The function helps distinguish between code that produces a value and code that executes an action, which is a fundamental concept in programming language semantics.