Filters in SL5
David R. Hanson · The Computer Journal · 1978
The filter facility of the SL5 programming language permits the programmer to attach a procedural component to a variable. This procedural component can be used to ‘filter’ values assigned to the variable or to filter the value of the variable whenever it is fetched. Filters are the basis for the inclusion, at the source language level, of such features as tracing, dynamic datatype checking, generators, and dynamic protection mechanisms. Most importantly, filters are used for argument binding, permitting various methods of argument transmission to be defined in SL5 itself. This paper gives an overview of SL5, describes the filter facility, and gives several examples of its use.