Abstract

This document is the first draft of a catalogue of refactorings for functional programs. Most are applicable to a variety of modern functional programming languages -- with the example code begin written in Haskell -- but some relate specifically to Haskell and are marked as such. What is Refactoring? Refactoring is `improving the design of existing code' and as such, it has been practised as long as programs have been written. It was first identified as an activity in its own right within the object-oriented programming community [3, 4] (http://www.refactoring.com). When does refactoring arise? To take an example, we might first program a system using an algebraic data type, and then decide to change the way that the data are represented. How should we proceed with this? One option is to modify the data type directly, that is to achieve the modification in a single step: this will require us to make substantial modifications to a program 's functionality and structure simultaneousl...

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