Polyvariant constructor specialisation

In his PEPM’93 paper Mogensen introduced a new off-line specialisation technique, constructor specialisation. What differentiates constructor specialisation from conventiomd specialisation techniques is the ability to specialise constructors. Like functions, constructors are specialised with respect to their static arguments. As these constructors are also part of a program’s type declaration, the effect of constructor specialisation is no longer limited to the algorithmic part of a program. Specializing constructors requires introducing new type definitions, specialised variants of the original definitions. The effect of constructor specialisation is, therefore, best understood as a combination of specialisation and a retyping transformation (changing the types of a program). In this paper we develop a new constructor specialiser that solves some of the remaining problems in [Mog93]. Moreover, we show that this specialiser provides an alternative solution for a problem in [Lau91b], where a mix-style [JSS89] specialiser failed to remove the projection-injection overhead from specialised versions of the specialiser.