# Suggestions for a parsing strategy? **URL:** \ **Category:** Ruby\ **Created:** [July 19, 2008, 5:05am UTC](https://www.ruby-forum.com/t/suggestions-for-a-parsing-strategy/143483 "2008-07-19T05:05:49Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![robb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/a183cd/32.png) [@robb](https://www.ruby-forum.com/u/robb)\ **Post date:** [July 19, 2008, 5:05am UTC](https://www.ruby-forum.com/t/suggestions-for-a-parsing-strategy/143483/1 "2008-07-19T05:05:49Z")
Hi all, I have input strings that can look like this: Common, Commerc(e, ial) I need to parse these into the three words that this represents: Common, Commerce, Commercial. I’m a little new to ruby, and hence wondering what direction would be best to go in? (.scan, regexes … something else?) For me, the complication I’m not sure how to deal with is the two “levels” of the comma as a separator. Thanks, Robb ---
**Author:** ![robb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/a183cd/32.png) [@robb](https://www.ruby-forum.com/u/robb)\ **Post date:** [July 19, 2008, 5:13am UTC](https://www.ruby-forum.com/t/suggestions-for-a-parsing-strategy/143483/2 "2008-07-19T05:13:25Z")
On Friday 18 July 2008 21:59:56 Robb wrote: > I’m a little new to ruby, and hence wondering what direction would be > best to go in? (.scan, regexes … something else?) For me, the > complication I’m not sure how to deal with is the two “levels” of the > comma as a separator. One way would be to find the exceptions first. Replace anything that matches the Commerc(e, ial) pattern with the two words, as the literal string “Commerce, Commercial”. Then you can just do a simple split on the commas, and maybe strip whitespace. ---
**Author:** ![robb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/a183cd/32.png) [@robb](https://www.ruby-forum.com/u/robb)\ **Post date:** [July 19, 2008, 5:44am UTC](https://www.ruby-forum.com/t/suggestions-for-a-parsing-strategy/143483/3 "2008-07-19T05:44:24Z")
On Fri, Jul 18, 2008 at 10:59 PM, Robb [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Hi all, > > I have input strings that can look like this: > > Common, Commerc(e, ial) > > I need to parse these into the three words that this represents: > > Common, Commerce, Commercial. This code does a lot of what you describe, providing the parenthetical only appears at the end. ==== s = “Common, Commerc(e, ial), Computer, Con(ic, ehead, temporary)” def parse\_word\_list(s) s.scan(/(\w+)(((.\*?)))?/).map { |root, junk, suffixes| [root, suffixes && suffixes.split(", ")] } end list = parse\_word\_list(s) # see what’s produced p list # use it to generate all words list.each do |root, suffix\_list| if suffix\_list suffix\_list.each do |suffix| puts “#{root}#{suffix}” end else puts root end end ==== Hope that helps, Eric ==== [LearnRuby.com](http://LearnRuby.com) offers Rails & Ruby HANDS-ON public & ON-SITE workshops. Please visit [http://LearnRuby.com](http://LearnRuby.com) for all the details. ---
**Author:** ![robb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/a183cd/32.png) [@robb](https://www.ruby-forum.com/u/robb)\ **Post date:** [July 19, 2008, 6:25am UTC](https://www.ruby-forum.com/t/suggestions-for-a-parsing-strategy/143483/4 "2008-07-19T06:25:57Z")
On Friday 18 July 2008 22:38:43 Eric I. wrote: > s.scan(/(\w+)(((.\*?)))?/).map { |root, junk, suffixes| This pattern looks really useful… Looking at the docs for scan, it looks like it can take a block. Which just leaves one question: Why isn’t this an Enumerator in Ruby 1.9? I don’t think the original meaning (of producing an array) is made much more difficult by the form s.scan(/…/).to\_a And I suspect that it would most often be useful for things like #map, if not used in block form outright. Making it an Enumerator would be somewhat more efficient than building a whole array first – and more responsive, if it’s a large string. ---
**Author:** ![robb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/a183cd/32.png) [@robb](https://www.ruby-forum.com/u/robb)\ **Post date:** [July 19, 2008, 1:45pm UTC](https://www.ruby-forum.com/t/suggestions-for-a-parsing-strategy/143483/5 "2008-07-19T13:45:20Z")
On Jul 19, 11:38 am, “Eric I.” [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > s.scan(/(\w+)(((.\*?)))?/).map { |root, junk, suffixes| s.scan(/(\w+)(?:((.\*?)))?/) can avoid the “junk” ^^,Your pattern is great & helpful ---
**Author:** ![robb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/a183cd/32.png) [@robb](https://www.ruby-forum.com/u/robb)\ **Post date:** [July 19, 2008, 1:07pm UTC](https://www.ruby-forum.com/t/suggestions-for-a-parsing-strategy/143483/6 "2008-07-19T13:07:28Z")
David M. wrote: > Why isn’t [the return value of scan] an Enumerator in Ruby 1.9? Or 1.8.7 for that matter. Yes, I’ve been asking myself this very same question since the release of 1.9. > And I suspect that it would most often be useful for things like #map, if > not used in block form outright. Making it an Enumerator would be somewhat > more efficient than building a whole array first – and more responsive, if > it’s a large string. Also it’d allow you to use the matchdata object inside map if you need to. The way it is now you’d have to do: string.enum\_for(:scan,/re/).map do md = Regexp.last\_match do\_something\_with md end instead of just string.scan.map do…end ---
**Author:** ![robb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/a183cd/32.png) [@robb](https://www.ruby-forum.com/u/robb)\ **Post date:** [July 19, 2008, 2:05pm UTC](https://www.ruby-forum.com/t/suggestions-for-a-parsing-strategy/143483/7 "2008-07-19T14:05:48Z")
> Making it an Enumerator would be somewhat more > efficient than building a whole array first – and more responsive, if it’s a > large string. There is also the StringScanner class that can be used to return one match at a time.