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Message from discussion Question on Grammar Specification
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LogicProgrammer  
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 More options Nov 18 2009, 7:32 pm
From: LogicProgrammer <logicprogram...@gmail.com>
Date: Wed, 18 Nov 2009 16:32:19 -0800 (PST)
Local: Wed, Nov 18 2009 7:32 pm
Subject: Re: Question on Grammar Specification
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Also, I understand how to parse a single string, but what I want to
parse an entire file?

Suppose that I had a rule which says something like this:

STATEMENT ::= TERM [, TERM]* '.'

i.e - a statement is a comma-delimited sequence of 1 or more terms
followed by period. And a program is defined as one or more
statements:

PROGRAM ::= STATEMENT+

On a successful parse I would like to get a list of all of the
"statement objects".

How would I attempt something like this?

Thanks again.

On Nov 18, 5:15 pm, LogicProgrammer <logicprogram...@gmail.com> wrote:

> Also if I want the the results of a parse to be represented as a
> string object, am I correct that I would append '> str' to the end of
> the corresponding grammar rule?

> On Nov 18, 5:13 pm, LogicProgrammer <logicprogram...@gmail.com> wrote:

> > Hi All,

> > I'm attempting to define a grammar for a simple logic programming
> > language. The initial portion of the EBNF is as follows:
> > (comments follow a %)

> > OBJECT    :== a-z[a-zA-Z0-9]*     %alpha-numeric string which begins
> > with a lower case letter
> > VARIABLE :== A-Z[a-zA-Z0-9]*    %alpha-numeric string which begins
> > with an uppercase letter
> > FUNC        :== OBJECT
> > TERM       :== OBJECT | VARIABLE | FUNC ( TERM [, TERM]* ) % term is
> > either an object, variable, or a function symbol of arity >= 1 -
> > parenthesis are literal tokens

> > PRED :== OBJECT
> > PREDSYM :== PRED | PRED ( TERM [, TERM]* )

> > To my understanding I should be able to use LEPL along the following
> > lines:

> > OBJECT = Token('[a-z][a-zA-Z0-9]*')
> > VARIABLE = Token('[A-Z][a-zA-Z0-9]+')
> > FUNC = OBJECT
> > TERM = Delayed()
> > TERM += OBJECT | VARIABLE | FUNC & '(' & TERM & ZeroOrMore(',' & TERM)
> > & ')'

> > etc.

> > For some reason though (probably a stupid mistake on my part) this
> > fails to parse the following:

> > parser = TERM.parse_string
> > TERM.parse("p(X)")

> > Am I doing something completely wrong?

> > Thank you kindly,
> > Gregory Gelfond


 
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