Taming E ects with MonadicTyping 1 Richard

The familiar Hindley-Milner type system of the ML language family is extended with monad annotations to account for possible side eeects of expression evaluation. This also allows eeects to be eeectively encapsulated by lexical scopes, with enforcement provided by type checking. A type-and-eeects analysis supports type inference. Type soundness and completeness theorems establish the coherence of monadic type inference with the reference semantics of a small ML-style language.