[Haskell-cafe] Using HList Records
rk at trie.org
Wed Aug 8 17:23:59 EDT 2007
Using The Darcs version of HList (http://darcs.haskell.org/HList/), I
can do simple things with (H)lists just fine, so
--angus = Key 42
-- .*. Name "Angus"
-- .*. Cow
-- .*. Price 75.5
-- .*. HNil
--main = putStrLn (show angus)
works, On the other hand examples from the HList paper for extensible
--key = firstLabel FootNMouth "key"
--name = nextLabel key "name"
--breed = nextLabel name "breed"
--price = nextLabel breed "price"
do not compile with errors
--Main.hs:15:8-17: Not in scope: `firstLabel'
--Main.hs:16:8-16: Not in scope: `nextLabel'
A quick show "ghc-pkg describe HList" shows that
--hidden-modules: Label4 CommonMain Variant GhcSyntax GhcRecord
-- Record HZip TIC TIP HTypeIndexed HOccurs HArray GhcExperiments
-- HListPrelude TypeEqBoolGeneric TypeEqGeneric1 TypeCastGeneric1
So the question is do I need to play around with the cabal file to
expose the right stuff? Or has the syntax changed?
I get errors running "./setup haddock" (configure, build, install, are
fine). Are the HList api docs available anywhere online?
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