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Refactoring Pattern Matching

Meng Wang‚ Jeremy Gibbons‚ Kazutaka Matsuda and Zhenjiang Hu

Abstract

Defining functions by pattern matching over the arguments is advantageous for understanding and reasoning, but it tends to expose the implementation of a datatype. Significant effort has been invested in tackling this loss of modularity; however, decoupling patterns from concrete representations while maintaining soundness of reasoning has been a challenge. Inspired by the development of invertible programming, we propose an approach to program refactoring based on a right-invertible language RINV - every function has a right (or pre-) inverse. We show how this new design is able to permit a smooth incremental transition from programs with algebraic datatypes and pattern matching, to ones with proper encapsulation, while maintaining simple and sound reasoning.

Journal
Science of Computer Programming
Month
January
Note
Revised version of the MPC2010 paper "Gradual Refinement"
Number
11
Pages
2216−2242
Volume
78
Year
2012