Re: Q: regarding regular grammars ...

Michael Roach wrote:
: > I thought regular expressions were regular grammars, is that assumption
: > wrong? And if so, could you explain the differences or point me to some
: > references. Thanks.


Karsten Nyblad (karsten@tdr.dk) wrote:
: Yes, it is wrong. Regular grammar are a superset of context free
: grammars
: (CFG). Even the class of langauges of CFG's is larger than the class of
: languages of regular expressions.


I think Karsten has misread the original question - Michael was
talking about regular grammars not context free grammars. Contrary to
Karsten's claim, regular grammars are a subset of CFG not a
superset. It is easy to convert from a RE to a RG grammar as long as
the RE doesn't use extended notions like variables (these things are
not really RE's, formally).


I find the Parsing Theory twin volume set recommended by Karsten good
for some theory but less good for everyday queries. The most readable
reference I know is Dick Grunne's book on parsing published a few
years ago by Ellis Horwood and now sadly out of print, but obtainable
from your library, perhaps? Personally I find the treatment in the
dragon book repetetive and disorganised.


                                                    Adrian


--
Dr Adrian Johnstone, Senior Lecturer in Computing, Computer Science Dep,
Royal Holloway, University of London, Egham, Surrey, TW20 0EX, England.
    Email a.johnstone@rhbnc.ac.uk Tel: 01784 443425 Fax: 01784 439786
--

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