From: nobu.nokada@...
Date: 2002-04-27T00:50:43+09:00
Subject: Re: expand_path and overlap

Hi,

At Sat, 27 Apr 2002 00:20:39 +0900,
Morris, Chris <chris.morris@snelling.com> wrote:
> 
> > I'm not sure, is this like what you want?
> > 
> >   def collapse_path(path, base)
> >     head, = path.split("/", 2)
> >     base.rindex(%r"(\A|.*/)#{Regexp.quote(head)}(?:/|\z)")
> >     ($1 or base) + path
> >   end
> 
> Thanks! It seems to be close -- though I haven't groked it myself to see
> where it's breaking down. First unit test fails:
> 
>   assert_equal("/a/b/c", collapse_path("b/c", "/a/b/c/d/e"))

Hmmm, it apparently passes.  Only 4th test failed.

def collapse_path(path, base)
  head, = path.split("/", 2)
  base.rindex(%r"(\A|.*/)#{Regexp.quote(head)}(?:/|\z)")
  ($1 or base.sub(%r|[^/]\z|, '\&/')) + path
end

if $0 == __FILE__
  require "test/unit"
  class TC_collapse_path < Test::Unit::TestCase
    def test_collapse_path
      assert_equal("/a/b/c", collapse_path("b/c", "/a/b/c/d/e"))
      assert_equal("/a/b", collapse_path("b", "/a/b/c/d/e"))
      assert_equal("/a/b/c/f", collapse_path("b/c/f", "/a/b/c/d/e"))
      assert_equal("/a/b/c/d/e/m/n/o", collapse_path("m/n/o", "/a/b/c/d/e"))
      assert_equal("/a/b/c/a/b/d", collapse_path("a/b/d", "/a/b/c/a/b/c"))
    end
  end
end

-- 
Nobu Nakada