Sprachen, Grammatiken und Transformationen 33 Evolution of Language Interpreters

Language-based tools involve some (ad-hoc) elements of a language's intended (say, formal) semantics. These elements relate to the specic service provided by a tool. For instance, a program analyser might implement a so-called abstract interpretation; a transformation tool might employ algebraic laws as well as typing and scoping rules; a translator implements the syntax-to-syntax edge in the commuting diagram with nodes for the two syntaxes and the two semantics of the involved languages. Type checkers and language interpreters can be seen as prototypical examples of language-based tools. Such tools implement the language semantics rather directly. The ex-tensibility of such semantics-oriented programs (and the underlying formal semantics descriptions) has received ample attention in the programming-language community