[Haskell-cafe] Deconstructing types

[Sean Leather]

> The answer is, I'm working on a recently semi-released package called
> TrieMap.
>
> The objective of this package, building off of the work in this paper<https://docs.google.com/Doc?docid=0AWuaUF8ZNTNDZHB3emdyaF8zMzNmZmtmcHo2Yw&hl=en>,
> is to automatically derive the type of a generalized trie for any algebraic
> type based on its algebraic representation.  (I am working on writing up my
> methods for publication.)
>
> Of course, if I could get automatic access to the mechanisms of a type's
> constructors, I wouldn't even require users to describe the algebraic
> representation of their type...


Well, it's relatively easy to use Template Haskell to determine the
structure of a datatype. Look in the "Generics" category on Hackage for a
number of examples (e.g. emgm, regular, multirec) or see if the Derive
package will do it for you. According to Neil Mitchell, you just need one
example:


http://www.cogsys.wiai.uni-bamberg.de/aaip09/aaip09_submissions/talk_mitchell.pdf

I don't know if it's easy or even possible to capture a sum-of-products view
from SYB.

Sean
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