System Description: Delphin – A Functional Programming Language for Deductive Systems

Delphin is a functional programming language [Adam Poswolsky and Carsten Schürmann. Practical programming with higher-order encodings and dependent types. In European Symposium on Programming (ESOP), 2008] utilizing dependent higher-order datatypes. Delphin's two-level type-system cleanly separates data from computation, allowing for decidable type checking. The data level is LF [Robert Harper, Furio Honsell, and Gordon Plotkin. A framework for defining logics. Journal of the Association for Computing Machinery, 40(1):143–184, January 1993], which allows for the specification of deductive systems following the judgments-as-types methodology. The computation level facilitates the manipulation of such encodings by providing facilities for pattern matching, recursion, and the dynamic creation of new parameters (which can be thought of as scoped constants). Delphin's documentation and examples are available online at http://delphin.logosphere.org.