Implementing Haskell: Language Implementation as a Tool Building Exercise

Although a number of tool boxes for compiler construction exist, the language implementation task can often be made easier by building specialised tools. A prototype Haskell system was implemented within a four month period using such an approach. The system is currently used as a front end for a transputer array, Haskell implementation. In this article we describe the tool building aspect of the implementation process. The little language tools, tree processing function generators and error message management routines developed are described. Although the tools are specific to this implementation, this mode of work can be worthwhile in a number of cases such as the implementation of novel languages, the targeting of unconventional architectures or, the experimentation with new implementation techniques. The lessons learned during this process are summarised and the specialised tool approach is evaluated.