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From: cs450a03@uc780.umd.edu
Newsgroups: comp.lang.apl
Subject: J 3.0 words BNF
Message-ID: <26MAR91.22244391@uc780.umd.edu>
Date: 26 Mar 91 22:24:43 GMT
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Experimenting with J to find out what its definition is is
educational, but at times I wish I had a more thorough definition of
what it's doing.

Of course, J changes so fast such things might be considered silly 8-)

Anyways, here's what I've come up with for what J is doing with the
words function (;:):

This is what you apply ;: to.  Result is a list of the words (in the
          same order they originally appeared).  As is usual for this
          sort of thing, rules apply to the largest sequence possible.

sentence =:: (BEGINING_OF_LINE *space *(word *space) END_OF_LINE)


word =:: [(alpha *[alpha numeric] *dot)
          (glyph *dot)
          (numeric *[alpha numeric] +dot)
          (numeric *[alpha (decimal numeric) numeric (space numeric)])
          (quote *[quotable (quote quote)] quote)]

---------------------------- character sets ---------------------------- 

alpha    =:: [a-zA-Z]
decimal  =:: [.]
dot      =:: [.:]
glyph    =:: [!-&(-,---/<-@[-`{-~]
numeric  =:: [_0-9]
quote    =:: [']
quotable =:: [^']
space    =:: [ \t]

Notes:  except for decimal, and quotable, all character sets are unique.
        I haven't tried control characters and ascii characters beyond
            ~, but I suspect they should be considered "glyphs"
        \t represents a tab character
        - between two characters represents a range of ascii characters 
        () indicates serial ordering
        [] indicates any of the options
        ^ indicates negation (all characters except following)
        * indicates 0 or more repetitions of next thing (yeah, I
            reversed it... seems easier to read though)
        + indicates 1 or more repetitions of next thing

Has anyone with 3.0 seen anything different from this?

Anybody from ISI care to comment on how stable this is likely to be?
(Yeah, I know, it's stable till it changes...)

Raul Rockwell