Abstract: Context Patterns, Part II

Functional languages allow the definition of functions by pattern matching, which performs an analysis of the structure of values. However, the structures which can be described by such patterns are restricted to a fixed portion from the the root of the value.

Context patterns are a new non--local form of patterns, which allow the matching of subterms without fixed distance from the root of the value.

Typical applications of context patterns are functions which search a data structure for patterns and transform it by replacing the pattern.

In this paper we introduce a new construct called extended context, which allows the definition of transformational functions without superfluous repetition of the recursive search.