Hi Cody..
I have to agree with Kaspar, this isn't what Parslet is for..
However...If I _had_ to get your parser to work..
1/ You are parsing (word | word space word)... Parslet will always consume
the first matching option.. so 'word' will match instead of 'word space
word'. Flip them to get 'word' to be the fallback option...
2/ there is ambiguity on the day (as it may be part of the name)... so I
would change the grammar to have "on" as your indicator that you are
starting a date... and 'at' to indicate a time. This would mean you can't
have someone called "on" as their last name... shame. With this (and you
assume your order is always the same... ie event_type, optional attendee,
date, time... ) then you can
rule(:attendee) { (word >> (space >> str('on').absnt? >> word ).repeat
).as(:attendee)}
<code>
require 'rubygems'
require 'parslet'
class SimpleParser < Parslet::Parser
rule(:space){str(" ")}
rule(:word) { match('\w').repeat(1) }
# rule(:attendee) { ((word >> space >> word )| word ).as(:attendee)}
rule(:attendee) { (word >> (space >> str('on').absnt? >> word
).repeat ).as(:attendee)}
rule(:event_type) { ( str('lesson') | str('class') | str('interview')
).as(:event_type) }
rule(:attendance) { str('with') >> space >> attendee}
rule(:stuff) {any.repeat}
rule(:temporality){ str('on') >> space >> stuff.as(:when) }
rule(:event) { event_type >> space >> attendance >> space >> temporality}
root(:event)
end
@parser = SimpleParser.new
require 'parslet/convenience'
# puts @parser.attendee.parse_with_debug("nigel thorne")
puts @parser.parse_with_debug("lesson with john doe on friday at
2:00pm")
</code>
... something like this
---
"No man is an island... except Philip"
On 13 December 2011 19:32, Kaspar Schiess <[email protected]> wrote:
> Hi Cody,
>
> The kind of sentences you're trying to match are highly ambiguous.
> Suppose you want to schedule dinner with Monday Doe, named after the day
> she was born? You will have to exclude all week-days from all names in
> order to even match names - and then clashes like this one are
> programmed to happen.
>
> If you look at the history of parsing, other formalisms than PEG have
> been developed for this kind of sentences. They use probabilistic and
> heuristic 'interpretation'-type approaches. [1] gives a good overview
> and many of these algorithms have been implemented in Ruby.
>
> Parslet implements PEG very slavishly, it doesn't even do whitespace
> ignore or left recursion. This is going to stay that way. PEG is very
> good (IMHO) for computer languages. It avoids many ambiguities by posing
> a formalism that doesn't allow them, which appeals to me because it is
> elegant.
>
> So that means: Parsing natural language with parslet will make you
> unhappy, folks! Cody, the common strategy for parsing things like this
> is to use a bottom up parser, LR(k) or the like. There are very elegant
> natural language frameworks out there as well. And last (but .. not
> least) there is chronic[2], which does part of what you want...
>
> regards,
> kaspar
>
> [1] http://en.wikipedia.org/wiki/Parser
> [2] http://rubygems.org/gems/chronic
> [3] http://duckduckgo.com/?q=natural+language+ruby
>
>
>
