Abstract programming supports the separation of logical concerns from issues of control in program construction. While this separation of concerns leads to reduced code size and increased reusability of code, its main disadvantage is the computational overhead it incurs. Fusion techniques can be used to combine the reusability of abstract programs with the efficiency of specialized programs.
Stratego is a language for program transformation based on the paradigm of rewriting strategies. In Stratego, transformation rules define basic transformation steps and user-definable strategies control the application of rules to a program. Since the problem-specific rules and the highly generic strategies which apply them are kept separate, these elements can be combined in a mix-and-match fashion to produce a variety of program transformations. In some instances this separation of concerns leads to inefficient implementations.
In this paper we show how such inefficiencies can be remedied using fusion. Furthermore, we show how fusion can be implemented using rewriting strategies by studying in detail the application of rewriting strategies to the fusion of the generic innermost strategy with sets of arbitrary-but-specific rewrite rules. Both the optimization and the programs to which the optimization applies are specified in Stratego.
The contributions of this work are twofold. In the first place, we show how to optimize and reason about rewriting strategies, which opens up a new area of strategy optimization. In the second place, we demonstrate how such optimizations can be implemented effectively using local, application-specific transformations. These techniques are applicable to transformation of programs in languages other than Stratego.
PatriciaJohann and EelcoVisser. Fusing Logic and Control with Local Transformations: An Example Optimization. In Workshop on Reduction Strategies in Rewriting and Programming (WRS'01), volume 57 of Electronic Notes in Theoretical Computer Science, Utrecht, The Netherlands, May 2001. Elsevier Science Publishers.
Abstract programming supports the separation of logical concerns from issues of control in program construction. While this separation of concerns leads to reduced code size and increased reusability of code, its main disadvantage is the computa- tional overhead it incurs. Fusion techniques can be used to combine the reusability of abstract programs with the efficiency of specialized programs.
In this paper we illustrate some of the ways in which rewriting strategies can be used to separate the de nition of program transformation rules from the strategies under which they are applied. Doing so supports the generic de nition of program transformation components. Fusion techniques for strategies can then be used to specialize such generic components.
We show how the generic innermost rewriting strategy can be optimized by fusing it with the rules to which it is applied. Both the optimization and the programs to which the optimization applies are speci ed in the strategy language Stratego. The optimization is based on small transformation rules that are applied locally under the control of strategies, using special knowledge about the contexts in which the rules are applied.
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