Expression-oriented programming language
[1] The typical exceptions are macro definitions, preprocessor commands, and declarations, which expression-oriented languages often treat as statements.[3] Critics, including language designers,[4][failed verification] blame expression-orientation for an entire class of programming mistakes wherein a programmer accidentally codes an assignment expression, which replaces a variable with an expression rather than testing it for equality with that expression.The designers of Ada and Java prevent this type of mistake by restricting control expressions to those that evaluate strictly to the boolean data type.[5][6] The designers of Python implemented assignment as a statement rather than an expression, thus prohibiting assignment from nesting inside any other statement or expression.[8]) In some expression-oriented languages, expressions that merely cause side effects return void types.