[Haskell-cafe] Named function fields vs. type classes
jgoerzen at complete.org
Tue Dec 14 09:47:21 EST 2004
I often have a situation where I'm designing specialized components to
do a more general task. Examples could include mail folder code (maildir,
mbox, etc), configuration file parsing, protocol handlers for URL
accesses, logging backends, etc.
For some of these, I've used a data object with named fields, each one
of them being a function that performs various tasks (open connection to
the URL, read data, whatever.) So, I get a standard interface. The
advantage of this approach is that I can build a list containing all
sorts of different data objects in it.
For others, I've used typeclasses, and made the different specialized
components a member of the typeclass. This seems to provide a cleaner
interface, and one that is more readily extended (maybe I want to
support IMAP folders, and support all its searching capabilities too).
On the other hand, it's difficult or impossible to make a list of a
bunch of different types of things that have nothing in common save
being members of the class.
Is there any advice on the best way to do these things?
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