Abstract. Refactoring is the process of improving the design of existing programs without changing their functionality. These notes cover refactoring in functional languages, using Haskell as the medium, and introducing the HaRe tool for refactoring in Haskell. 1

In this paper, we propose a new method, based on the use of temporal logic, for developing and reasoning about functional programs. Our software development method is rigorous and systematic: starting with a list of informal requirement descriptions, we initially derive a set of object-based specifications, which are later on transformed into modular monadic functional programs. The obtained specifications and programs are shown to consist in an effective basis for verification.