PROLOG GRAMMAR-RULE TRANSLATOR
                              Jocelyn Paine
                   Shelved on the 6th of December 1987
           (Contribution by Richard O'Keefe sent in July 1988)


The entry comes as four files:

    GRAMMAR.PRE     - this file
    GRAMMAR.PL      - the source
    GRAMMAR_OK.PL   - a different translator from Richard O'Keefe
    GRAMMARBUG1.    - a note of suspected bugs from Richard O'Keefe


GRAMMARBUG1. is  a short message -  Richard warns of two  bugs which may
afflict GRAMMAR.PL. I haven't yet tested it for them. GRAMMAR_OK.PL is a
new translator he wrote, which eliminates  these and some other bugs. It
is commented.

Until  I examine  them properly,  that's  all I'll  say about  Richard's
files. The rest of this note describes GRAMMAR.PL.


This  program defines  a predicate,  'grexpand', for  expanding Definite
Clause Grammar Rules into Prolog clauses. These are the standard form of
DCG rules, for which a translator is built-in to many Prologs.

It also  defines 'phrase',  for parsing  a list  according to  a grammar
rule.

It  does  not contain  predicates  for  reconsulting files  and  calling
'grexpand' on each term.


The translator is essentially the same as that published in "Programming
in Prolog", by Clocksin and Mellish.


To use the program, call 'grexpand' and 'phrase'!

The code may be useful when building other grammar-directed systems, for
example, syntax-directed formatters.


Note that  the program includes  'append' and 'islist';  utilities which
you may have elsewhere.


CHECKED ON EDINBURGH-COMPATIBLE (POPLOG) PROLOG : yes.

PORTABILITY : easy, no known problems.

INTERNAL DOCUMENTATION : comments for each predicate, sample output.