SLIP is a list processing

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, invented by

Joseph Weizenbaum Joseph Weizenbaum (8 January 1923 – 5 March 2008) was a German American computer scientist and a professor at MIT. The Weizenbaum Award is named after him. He is considered one of the fathers of modern artificial intelligence. Life and care ...

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 ALGOL (; short for "Algorithmic Language") is a family of imperative computer programming languages originally developed in 1958. ALGOL heavily influenced many other languages and was the standard method for algorithm description used by th ...

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ELIZA ELIZA is an early natural language processing computer program created from 1964 to 1966 at the MIT Artificial Intelligence Laboratory by Joseph Weizenbaum. Created to demonstrate the superficiality of communication between humans and machines ...

, an early

natural language processing Natural language processing (NLP) is an interdisciplinary subfield of linguistics, computer science, and artificial intelligence concerned with the interactions between computers and human language, in particular how to program computers to proc ...

computer program A computer program is a sequence or set of instructions in a programming language for a computer to execute. Computer programs are one component of software, which also includes documentation and other intangible components. A computer progra ...

created by Weizenbaum at the

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General overview

In a nutshell, SLIP consisted of a set of FORTRAN "accessor" functions which operated on circular doubly linked lists with fixed-size data fields. 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

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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 state history stack—a good example of a

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—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. * '' Computer Power and Human Reason: From Judgment To Calculation'', Joseph Weizenbaum, San Francisco: W. H. Freeman, 1976 Fortran libraries Programming languages {{compu-lang-stub