sort(cmp=func)

[Daniel Fetchinson]

> I have a list of objects that generate code.  Some
> of them depend on others being listed first, to
> satisfy dependencies of others.
>
> I wrote a cmp function something like this:
>
> def dep_cmp(ob1, ob2):
> 	
> 	if ob1.name in ob2.deps:
> 		return -1
> 	else:
> 		return 1
>
> I also tried returning 0 when there were no dependency
> relationships between the objects.
>
> This failed, because every object was not compared with
> ever other.  I imagine that this is because sort assumes
> that if a > b and b > c, then a > c.  In my case, this
> isn't really true.  If a is not dependent on b, and
> b is not dependent on c, that doesn't mean that a is not
> dependent on c.
>
> Is there a better way?

It's only meaningful to talk about sorting if your particular
definition of "<" is transitive. I.e. a < b and b < c should imply a <
c. If this is not satisfied, it doesn't make sense to sort according
to your "<" definition. It's just not a well-defined operation and no
trick will make it work.

Cheers,
Daniel
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