Re: "mini" pascal by Wirth (A Johnstone)
Mon, 20 Mar 1995 08:10:11 GMT

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Newsgroups: comp.compilers
From: (A Johnstone)
Keywords: Pascal
Organization: Royal Holloway, Univ of London
References: 95-03-027 95-03-085
Date: Mon, 20 Mar 1995 08:10:11 GMT

Feliks Kluzniak ( wrote:
: There is also another "simplified Pascal" by Wirth, which is a much
: more complete language than PL0. It is called Pascal-S and is
: described in Wirth's contribution to D. W. Barron (ed.): Pascal - The
: Language and Its Implementation. John Wiley & Sons, Chichester, 1981

Some years ago we went to the troble of typing Pascal-S in and making
it go (this was in the days before international networks :-(. If
anybody wants a copy of the source code then please mail me.

BTW an interesting problem we had was that at first the parser
wouldn't work. Like most of Wirth's compilers the keywords are kept in
an array in alphabetical order and then each alphanumeic ID is checked
using a binary search on the table. Unfortunately on the machine that
Pascal-S was developed for DOWNTO came before DO in the lexicographic
ordering (or do I mean the other way round) although all compilers I
have tried it on do it the the normal way round. You might want to
watch out for this `error' in the source code if you try and work from
the paper.

    Dr Adrian Johnstone, Dean of the Science Faculty, Dept of Computer Science,
        Royal Holloway, University of London, Egham, Surrey, TW20 0EX, England.
Email: Tel: +44 (0)1784 443425 Fax: +44 (0)1784 443420

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