From: 7stud -- <bbxx789_05ss@...>
Date: 2007-10-27T06:38:08+09:00
Subject: Re: Newlines included in bracket negation

Chris Morris wrote:
> (... that subject probably makes no sense ...)
> 
> Anyway, I have some unexpected (to me) behavior in the following regexp.
> This example is contrived, but based on a real need. Can anyone explain 
> why
> the result is multi-line, even though the re is not?
> 
> require 'test/unit'
> 
> class TestRE < Test::Unit::TestCase
>   def test_newlines
>     src = "happy\n\nbirthday"
>     assert_equal("hday", src.scan(/h[^x]*?day/).to_s)
>   end
> end
> 
> produces
> 
> Finished in 0.031 seconds.
> 
>   1) Failure:
> test_newlines_consumed_in_not_section(TestRE) ...
> <"hday"> expected but was
> <"happy\n\nbirthday">.

> Can anyone explain why
> the result is multi-line, even though the re is not?

It's not a question of the re being multi-line or not, it's a question 
of the re being greedy v. non-greedy.  But because there is only one 
match for your regex, the issue of greedy v. non-greedy is irrelevant.

If you think about it, there is really no concept of 'lines' with 
regards to text.  There really is only one line--one, long, continuous 
line of characters.  Some of those characters might be '\n' characters, 
and we may choose to interpret a '\n' as a new line, but that doesn't 
change the fact that there is still just one continuous string of 
characters.  A regex has nothing inherently programmed into it that will 
cause it to stop looking for matches when a '\n' is encountered in the 
sequence of characters.   The  regex  character '.' will stop searching 
at a newline, but that is not true of regex's generally.  In any case, 
you do not use the '.' character in your regex, so that behavior is 
irrelevant.
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