SLIP (programming language)

SLIP is a list processing computer programming language, invented by Joseph Weizenbaum in the 1960s. The name "SLIP" stands for Symmetric LIst Processor. It was first implemented as an extension to the Fortran programming language, and later embedded into MAD and ALGOL. [ [http://www.heuse.com/s.htm Computer Programming Languages - S ] ]

General Overview

In a nutshell, SLIP consisted of a set of FORTRAN "accessor" functions which operated on doubly-linked circular lists with a fixed payload size. The "accessor" functions had direct and indirect addressing variants.

List Representation

The list representation had four types of cell: a reader, a header, a sublist indicator, and a payload cell. The header included a reference count field for garbage collection purposes. The sublist indicator allowed it to be able to represent nested lists, such as (A, B, C, (1, 2, 3), D, E, F) where (1, 2, 3) is a sublist indicated by a cell in the '*' position in the list (A, B, C, *, D, E, F). The reader was essentially a history list or ordered collection of Mementos, where each cell pointed to the header of the list being read, the current position within the list being read, and the level or depth of the history stack.

References

* "Symmetric List Processor", Joseph Weizenbaum, CACM 6:524-544(1963). Sammet 1969, p.387.
* "", Joeseph Weizenbaum, San Francisco: W. H. Freeman, 1976 ISBN 0-7167-0463-3