Regarding Class Aliases

[Christophe Poucet]

Dear all,

I have looked through the tickets of haskell-prime.  I would like to bring
up my own point of view concerning one specific ticket, namely Class
Aliases.  I have looked at the ticket and right now it's marked as a low
priority with low probability of entering the standard.

As I see it, class aliases have a low impact on most of the code, only
requiring some syntactical changes and some extensions in .hi interface.
However, they can be very empowering with regards to the modularisation of
type classes.  Often people on #haskell want to implement some subset of Num
and reuse as much as possible that which exists but find themselves stuck
because their type does not support all the semantics of Num.  With the use
of type-classes one can easily decompose Num into a set of subclasses
without making it more difficult to use for the general user of Num.  In
addition it can be used for other modularisations as well, making them quite
trivlal, for instance the proposal to split Enum.

Just my two cents :)
With regards,
Christophe Poucet


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Christophe Poucet
Ph.D. Student
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E-mail: Christophe.Poucet at imec.be
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