Is there an interpreter (or compiler) for untyped lambda calculus? (According to this thread it's possible.) I recognize that it would be of little use as a programming language, particularly if much of the language (such as numerals and boolean operators) were implemented (either by the user or by a library) in the language itself. However, I still think it would be a fun tool useful for learning and exploring the calculus. For this an interpreter would be preferable to a compiler, tho either would work. Does anyone know of such a program?
Benjamin Pierce provides implementations of the untyped and simply-typed λ-calculus that accompany his textbook Types and Programming Languages. They are written in OCaml and include example definitions. It shouldn't be difficult to write an interpreter or compiler for simple λ-calculi, however.