A transformation for implementing on-demand strategy annotations

Authors

María Alpuente, Santiago Escobar, and Salvador Lucas

Abstract

Strategy annotations are used in eager programming languages (e.g., OBJ2, OBJ3, CafeOBJ, and Maude) for improving efficiency and/or reducing the risk of nontermination. Syntactically, they are given either as lists of natural numbers or as lists of integers associated to function symbols whose (absolute) values refer to the arguments of the corresponding symbol. A positive index enables the evaluation of an argument whereas a negative index means ``evaluate on-demand''. Recently, we have introduced a formal description of the operational meaning of such on-demand strategy annotations which improves previous formalizations that were lacking satisfactory computational properties. Moreover, currently there is no implementation supporting computations under on-demand strategy annotations. In this paper, we introduce a program transformation which can be computed automatically, in such a way that the use of on-demand strategy annotations becomes possible for programs which are then correctly executed in typical OBJ interpreters.