Computer support for students’ work in a formal system: MacCPICT

MacPICT is an interactive program written in LPA Prolog which has encoded within it the rules of Martin‐L#auof’ s constructive type theory #opCTT#cp, a formal system based on constructive or intuitionistic mathematics. It allows us to specify and express any total, computable function, so from a computer science point of view we can write both specifications and programs, along with the derivations which lead from one to the other, in a single language. It can also be used, via the ‘logical’ interpretation, to support construction of derivations in a course which teaches intuitionistic, propositional, first‐ or higher‐order logic. MacPICT is a reconstruction of PICT #ob1#cb and is intended to support the teaching of CTT. It has been developed and improved over the last five years, during which time it has been used to support teaching in an MSc. course. In this paper I show how MacPICT can be used for supporting derivations in CTT, by way of detailed examples, and suggest some further problems the reader ...