Not sure the proposal helps me with my other issues. The appealing
thing about hlists is that labels are first class which means obvious
ways of parsing URLEncoded Strings and obvious ways to render them in
XML. In particular HLists are actually a different type from
positional data declarations and that is good.
-Alex-
On Wed, 21 Mar 2007, Jules Bean wrote:
S. Alexander Jacobson wrote:
Conceptually, I think what I really want is the data structure equivalent
of type inference. Just as I don't want to be forced to declare my
function types, I don't want to be forced to declare my data types. The
field labels I use should be enough to define the shape of my type. The
reason this is really important is that if hlists contain hlists, the type
declarations can get really really messy
Separately, I would really like hrecords not to have order dependency. It
seems strange to me that (Foo .*. Bar .*. HNil) is a different type from
(Bar .*. Foo .*. HNil).
These particular two issues : type inference based on record 'shape' and
records without order dependency, (ignoring the SYB part of the problem for
the moment) are both addressed in the following haskell records proposal
(and, undoubtedly, others)
http://research.microsoft.com/~simonpj/Haskell/records.html
Jules
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