From: Francis Hwang <sera@...>
Date: 2005-02-14T02:02:16+09:00
Subject: Re: "Joining" strings which may be nil (or) Handling Option hashes

On Feb 13, 2005, at 11:44 AM, Robert Klemme wrote:
> Lots of, here are some:
>
>>> opts = {"title"=>"ruby", "author"=>"dave", "publisher"=>"oreilly", 
>>> "foo"=>nil}
> => {"title"=>"ruby", "author"=>"dave", "foo"=>nil, 
> "publisher"=>"oreilly"}
>>> opts.select{|k,v|v}
> => [["title", "ruby"], ["author", "dave"], ["publisher", "oreilly"]]
>>> opts.select{|k,v|v}.map{|k,v| "#{k}=#{v}"}.join(" and ")
> => "title=ruby and author=dave and publisher=oreilly"
>
> Here's a more efficient variant - using #inject of course :-)
>
>>> opts.inject(nil){|s,(k,v)| v ? (s ? s << " and " : "") << k << "=" 
>>> << v : s}
> => "title=ruby and author=dave and publisher=oreilly"

Maybe the OP isn't worried about this, but: Is there a way to represent 
ORs as well as ANDs if you're doing this?

Francis Hwang
http://fhwang.net/