Programming Languages and Compilers Commons^™

Pattern Synonyms, Matthew Pickering, Gergő Érdi, Simon Peyton Jones, Richard A. Eisenberg

Computer Science Faculty Research and Scholarship

Pattern matching has proven to be a convenient, expressive way of inspecting data. Yet this language feature, in its traditional form, is limited: patterns must be data constructors of concrete data types. No computation or abstraction is allowed. The data type in question must be concrete, with no ability to enforce any invariants. Any change in this data type requires all clients to update their code.

This paper introduces pattern synonyms, which allow programmers to abstract over patterns, painting over all the shortcomings listed above. Pattern synonyms are assigned types, enabling a compiler to check the validity of a …