Stratego is a lenguage for the specification of transformation rules and strategies for applying them.The basic actions of transformations are matching and building instantiations of first-order term patterns.The language supports concise formulation of generic and data type-specific term traversals.One of the unusual features of Stratego is the separation of scope from matching,allowing sharing of variables through traversals.The combination of first-order patterns with strategies forms and expressive formalism for pattern mathcing.In this paper we discuss three examples of strategic pattern matching:(1) Contextual rules allow matching and replacement of a pattern at an arbitrary depth of a subterm of the root pattern.(2) Overlays serve to hide the representation of a language in another (more generic) language.These techniques are illustrated by means of specifications in Stratego.
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