ALF ("Another logical framework") is a structure editor for monomorphic Martin-Löf type theory developed at Chalmers University. It is a predecessor of the Alfa, Agda, Cayenne and Rocq proof assistants and dependently typed programming languages. It was the first language to support inductive families and dependent pattern matching.
References
Further reading Lena Magnusson and Bengt Nordström. "The ALF proof editor and its proof engine". Thorsten Altenkirch, Veronica Gaspes, Bengt Nordström and Björn von Sydow. "A user's guide to ALF".
External links Alfa