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From: jeff@aiva.ed.ac.uk (Jeff Dalton)
Newsgroups: comp.lang.misc,comp.lang.lisp
Subject: Re: reflexivity
Keywords: reflexivity,meta-circularity
Message-ID: <618@aiva.ed.ac.uk>
Date: 12 Oct 88 21:06:12 GMT
References: <612@crin.crin.fr> <826@etive.ed.ac.uk>
Reply-To: jeff@uk.ac.ed.aiva (Jeff Dalton)
Organization: Dept. of AI, Univ. of Edinburgh, UK
Lines: 40

In article <826@etive.ed.ac.uk> sean@lfcs.ed.ac.uk (Sean Matthews (AI)) writes:
>In article <612@crin.crin.fr> napoli@crin.crin.fr (Amedeo NAPOLI) writes:
>>Does anybody have clear definition of the following terms:
>>- meta-circularity
>>- reflexivity, self-reflexivity
>>for a language ?

>>Are there good (and easy to read) references on these or related topics ?

>reflection is where a programming language has access to its own interpreter,
>and can modify it.  [3 references follow]

The following may also be of interest:

   Alan Bawden.  Reification without Evaluation.  Proceedings of the
   1988 ACM Conference on Lisp and Functional Programming, p. 342ff.

The abstract begins:

   Constructing self-referential systems ... is actually more
   straightforward than you think.

Meta-circularity: a meta-circular interpreter for a language is
just an interpreter written in that language.  Textbook Lisp
interpreters typically have that property.  In particular, if
they implement a subset of some Lisp dialect they tend to be
written in that subset.

So meta-circularity is just the property of being implemented
by using the construct being implemented.

A good reference is:

   J. C. Reynolds.  Definitional Interpreters for Higher-order
   Programming Languages.  Proceedings of the ACM National
   Conference 1972, pp 717-740.

Jeff Dalton,                      JANET: J.Dalton@uk.ac.ed             
AI Applications Institute,        ARPA:  J.Dalton%uk.ac.ed@nss.cs.ucl.ac.uk
Edinburgh University.             UUCP:  ...!ukc!ed.ac.uk!J.Dalton