Notes for pipelines of transformations for MLF

These notes attempt to survey basic manipulations that can be done to a ML functional program prior to compilation. The paper does not consider transformations for improvement of the code but it only considers manipulations of the source text which can allow the compiler to do a better job. Which manipulationto choose depends on the target language. The survey can be useful for answering the above question and hence for choosing a convenient pipeline of transformations to prepare translation towards a given target language. Functional program transformation modiies the whole structure of a functional program in order to facilitate the production of a better code. It can also make the program use less memory. Functional programs have a precise mathematical semantic which allows to use source to source transformation techniques in order to provide any semantically correct desired form of program. In this paper, we address a catalog of eager semantic transformations on a functional language like ML. We consider only here fully automatic program transformation. Most of these transformations are usually well known though it can happen that the paper makes some contribution in some of the transformations that are described. The goal of the paper consists mostly in classifying basic transformations and in seeing how they can be combined into diverses transformation strategies. It might happen that the transformation strategy we describe as a composition of basic transformations could be expressed directly in a more speciic and eecient algorithm. However the division into basic parts makes the transformation toolkit which is proposed in the paper very exible and reusable. 1 A transformation strategy serves a certain purpose. The concern can be the target language of the translation. For example, monomorphization is a useful transformation if the target language is a nonpolymorphic language, and defunctionalization is useful if the target language is rst order, and lambda-lifting is useful if the target language is a term rewriting system. The sole concern can be optimization. In this case, transformation strategies such as deforestation or tuppling are useful. Another concern can be the model of the implementation sequential or parallel or distributed. In this paper, we limit ourselves to some transformation strategies of the rst category. Some basic transformations are easily recognized as belonging in a spe-ciic strategy but they can also be used as steps in other strategies. For example a type enumeration can be a step for a monomorphization but …