An Expression Processor: A Case Study in Refactoring Haskell Programs

Refactoring is the process of changing the structure of a program while preserving its behaviour. This behaviour preservation is crucial so that refactorings do not introduce any bugs. Refactoring is aimed at increasing code quality, programming productivity and code reuse. Refactoring has been practised manually by programmers for as long as programs have been written; however, with the advent of refactoring tools, refactoring can be performed semi-automatically, allowing refactorings to be performed (and undone) easily. In this paper, we briefly describe a number of refactorings implemented in the Haskell Refactorer, HaRe. In addition to this, we also implement a simple expression processor to demonstrate how some of the refactorings implemented in HaRe can be used to aid programmers in developing Haskell software.