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 in order to increase code quality, programming productivity and code reuse. 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 new refactorings for Haskell 98 programs implemented in the Haskell Refactorer, HaRe. In particular, a number of new structural and data-type refactorings are presented. We also implement a simple expression processor, clearly demonstrating how the refactorings and the HaRe tool can aid programmers in developing Haskell software. We conclude the paper with a discussion of the benefits of refactoring Haskell programs, together with their implementation and design limitations.

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