From: Massimiliano Mirra <list@...>
Date: 2002-09-17T10:30:30+09:00
Subject: Re: Dependency "trees" - suggestions?

On Tue, Sep 17, 2002 at 03:33:24AM +0900, GOTO Kentaro wrote:
> > So this is a DAG "Directed Acyclic Graph" for which there many algorithms
> > available.
> FYI: Ruby 1.7.x has tsort.rb as a standard library.  

*Sound of head banging against the wall*

Why do I always wait so long before asking the List?

tsort.rb looks just like the perfect solution for the lazy me.  I
particularly like this:

    "If there is a cycle, (({TSort::Cyclic})) is raised."

:-)

I'm trying it in 1.6 and I get two test failures.  This is the first:

Failure occurred in test_cycle(TSortTest) 
  [/home/bard/lib/ruby/runit/assert.rb:56]: Expected exception to
  be of type <TSort::Cyclic> but was <LocalJumpError: no block given


    def test_cycle
      h = {1=>[2], 2=>[3, 4], 3=>[2], 4=>[]}
      assert_equal([[4], [2, 3], [1]],
        h.strongly_connected_components.map {|nodes| nodes.sort})
      assert_exception(TSort::Cyclic) { h.tsort }  # <-----
    end


I looked at TSort::tsort but couldn't see where a block was required.


Massimiliano