[darcs-users] [patch21] remove trailing whitespace (and 2 more)

[Ganesh Sittampalam]

On Tue, 3 Nov 2009, Kamil Dworakowski wrote:

>>> Sun Oct 25 12:29:54 GMT 2009  Kamil Dworakowski <kamil at dworakowski.name>
>>>  * resolve issue1636: match hunk
>>>
>>>  A new primitive match type.
>>
>> My second point of discussion is about the implementation. What you've done
>> makes sense to me and fits in well with the list_touched_files code. But
>> both your code and list_touched_files add to the Patchy class (and
>> various instances) and it feels like a bit of an abstraction violation, and
>> also rather boilerplatey. I have a feeling we should somehow generalise
>> using some form of generic programming library before it gets out of hand,
>> but I'm not experienced enough with them to pick one or map out what the
>> solution would look like.
>
> It seems to me that both the operations, list_touched_files and
> hunkMatches, map Prim to some Monoidal value, and for every other
> instance of Patchy they just mconcat from the children. Maybe adding a
> method that takes a function returning a monoidal value for a Prim
> would be good enough to express both list_touched_files and
> hunkMatches. What do you think?

That sounds like a good idea. It doesn't resolve my concern about 
abstraction violation, but I'm not really sure that's such a big deal 
given that Prim is an important kind of patch.

In fact, we could just have something that returns a list of Prim, which 
is equivalent but simpler. The only reservation I have is that any clients 
that need more intelligent handling of conflictors than just sticking all 
the pieces together wouldn't be able to use it, but since they don't exist 
right now it's not really worth worrying about.

Cheers,

Ganesh