wrong sorting example for topological-sort

[Christian Kellermann]

As found by "WJ" on comp.lang.scheme:

(topological-sort
 '((i am)
   (not trying)
   (confuse the)
   (am trying)
   (trying to)
   (am not)
   (trying the)
   (to confuse)
   (the issue))
  eq?)

 ===>
(not i am trying to confuse the issue)


The correct output is:

(i am not trying to confuse the issue)

[Moritz Heidkamp]

This happens because the dependencies of am are defined twice, one of them clobbering the others. I think we have three options:

1. Throw an error in that case
2. Document it as undefined behavior
3. Concatenate the dependencies

What do you think would be the most reasonable thing?

[Moritz Heidkamp]

Here's the patch implementing option 3 as discussed on IRC.

[felix winkelmann]

Pushed in b175ce65fe17c0887ed89f070dc4c16ef95d51f9. Note that I had to change one test result which may be a user-visible change, which I consider acceptable as the new order seems more natural.

[Mario Domenech Goulart]

This fix exposed issues in some eggs:

• callable-data-structures (fixed)
• generics (patch submitted)
• pigeon-hole (patch submitted)
• r7rs (fixed)
• xml-rpc (patch submitted)

I'm documenting the status of eggs here so that we don't duplicate work.