From: Warren Brown <warrenbrown@...>
Date: 2005-09-28T23:58:56+09:00
Subject: Re: Splitting a string with escapable separator?

Jason,

>> I'm trying to come up with an *elegant* way to split
>> a string into an array at a separator with the
>> additional feature that the separators can be
>> escaped.

> With the new Regex engine in cvs ruby you can use a
> negative lookback assertion in your split:
> >> s = "Hello\\, World, Hi"
> => "Hello\\, World, Hi"
> >> s.split /(?<!\\),/
> => ["Hello\\, World", " Hi"]

    With the current Ruby RE engine, you can use zero-width positive
lookahead if you don't mind reversing the string before and after the
split:

irb(main):001:0> s = "Hello\\, World, Hi"
=> "Hello\\, World, Hi"
irb(main):002:0> s.reverse.split(/,(?!\\)/).map {|ss| ss.reverse}
=> [" Hi", "Hello\\, World"]

    You might also consider handling escaped escape characters by
ignoring pairs of escape characters:

irb(main):003:0> s = "Test, Test\\, Test\\\\, Test\\\\\\, Test"
=> "Test, Test\\, Test\\\\, Test\\\\\\, Test"
irb(main):004:0> s.reverse.split(/,(?!(\\\\)*\\([^\\]|$))/).map {|ss|
ss.reverse}
=> [" Test\\\\\\, Test", " Test\\, Test\\\\", "Test"]

    I hope this helps.

    - Warren Brown