The Design of Monty: a Programming/Scripting Language

This paper describes the design of Monty, a language intended to be equally suitable for both scripting and conventional programming. Monty features an unusually flexible type system in which all values are viewed as objects in a single-inheritance class hierarchy, static and dynamic typing are smoothly integrated, and both nonvariant and covariant generic classes are supported. An interesting byproduct of the design of Monty has been the light it has shed on the power of mutability as a linguistic concept. Among other things, it turns out that the type-soundness of a covariant generic class is closely related to the class's mutability.