Abstract

Building on a judgmental formulation of lax logic, we propose a modal language which can be used as a framework for practical programming languages with e#ects. Its characteristic feature is a syntactic distinction between terms and expressions, where terms denote values and expressions denote computations. We distinguish between control e#ects and world e#ects, and allow control e#ects only in terms and world e#ects only in expressions. Therefore the distinction between values and computations is made only with respect to world e#ects. We give an explanation of the type system and the operational semantics from a modal logic perspective. We also introduce a term construct similar to Haskell's runST construct and augment the type system to ensure its safety.

Citations