[darcs-users] darcs patch: Fix a memory leak in Darcs.Repository.Repair.

Eric Kow kowey at darcs.net
Tue Dec 23 10:31:31 UTC 2008


On Tue, Dec 23, 2008 at 00:59:15 +0000, Ganesh Sittampalam wrote:
> Just to give a (very brief!) overview of the point of IsEq: the type 
> witnesses stuff is designed so that the type system generally knows when 
> two patch contexts are the same, because they are represented by the same 
> type witness. Sometimes, this information (namely the equality of two 
> contexts) has to be propagated around the darcs code to help the type 
> system out, and the way we do this is with IsEq, which amounts to evidence 
> that two type witnesses with different names are actually the same. The 
> point about it is the declaration:
> 
> data EqCheck a b where
>    IsEq :: EqCheck a a
>    NotEq :: EqCheck a b
> 
> so if we have some value of type EqCheck a b in our hands, and we inspect 
> it and it turns out that it is 'IsEq', then we have a proof that a = b.

I've posted a link on this to the wiki, thanks!

http://wiki.darcs.net/index.html/DarcsInternals

-- 
Eric Kow <http://www.nltg.brighton.ac.uk/home/Eric.Kow>
PGP Key ID: 08AC04F9
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