Editing Extensible programming (section)

=== Death of the historical movement ===
Standish attributed the failure of the extensibility movement to the difficulty of programming successive extensions. A programmer might build a first shell of macros around a base language. Then, if a second shell of macros is built around that, any subsequent programmer must be intimately familiar with both the base language, and the first shell. A third shell would require familiarity with the base and both the first and second shells, and so on. Shielding a programmer from lower-level details is the intent of the [[Abstraction (computer science)|abstraction]] movement that supplanted the extensibility movement.

Despite the earlier presentation of Simula as extensible, by 1975, Standish's survey does not seem in practice to have included the newer abstraction-based technologies (though he used a very general definition of extensibility that technically could have included them). A 1978 history of programming abstraction from the invention of the computer until then, made no mention of macros, and gave no hint that the extensible languages movement had ever occurred.<ref name="Guarino1978">Guarino, L.R., "[https://cds.cern.ch/record/119689 The Evolution of Abstraction in Programming Languages]", ''CMU-CS-78-120'', Department of Computer Science, Carnegie-Mellon University, Pennsylvania, 22 May 1978.</ref> Macros were tentatively admitted into the abstraction movement by the late 1980s (perhaps due to the advent of [[hygienic macros]]), by being granted the pseudonym ''syntactic abstractions''.<ref name="Gabriel1989">Gabriel, Richard P., ed., "[https://dl.acm.org/citation.cfm?id=66092 Draft Report on Requirements for a Common Prototyping System]", ''SIGPLAN Notices'' 24 no. 3 (March 1989), pp. 93ff.</ref>