Extensible languages

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Last modified: 05-Jul-07.

Some mention should be made of "extensible" languages, a trend that seems to have reached its height with two symposia circa 1970, [Chri 69, Schu 71].  The general idea was that the programmer would be given the means to construct a specialized language for any arbitrary application area by extending a base language.  In practice, the name "extensible languages" was applied to everything from SIMULA, to PL/I (because of its bewildering macro facility), to compiler-compilers.  The trend lost momentum after the symposia; see [Stan 75].

Although the concept of extensible languages appears quite similar to the adaptivity principle, very little of the research done was accompanied by formal grammar models.  An exception is Wegbreit's ECFGs; W-grammars might also be excepted, since ALGOL 68 was painted as an extensible language in the earlier of the two symposia.  Also, a pathological case was the extensible language AEPL, in which the language processor was driven by a dynamically modifiable set of Chomsky type 0 grammar rules with programs attached to them.

See also:  Wikipedia article "Extensible programming".

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