duncan.coutts at worc.ox.ac.uk
Thu May 8 19:07:42 EDT 2008
On Thu, 2008-05-08 at 15:39 -0700, Isaac Potoczny-Jones wrote:
> Duncan Coutts wrote:
> > Does this seem like a good idea? What is/was the rationale for tags in
> > the first place?
> Yes, if I recall, Tags were not originally supposed to affect the
> ordering of versions,
And actually they don't affect the ordering but they do affect equality.
Yes it's inconsistent.
If we look in the base library in Data.Version we find:
instance Eq Version where
v1 == v2 = versionBranch v1 == versionBranch v2
&& sort (versionTags v1) == sort (versionTags v2)
-- tags may be in any order
instance Ord Version where
v1 `compare` v2 = versionBranch v1 `compare` versionBranch v2
This is clearly wrong. We would expect that:
a == b
<=> compare a b == EQ
but that does not hold here.
> but meant only for human consumption. Whether
> changing that now is a good idea or not, it's hard to say. How many
> packages in Hackage have any tags, for instance?
One. It was uploaded the other day which is why I just noticed that it's
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