Thanks a lot, Stephen - was just about giving up on this.
The correct type signature turned out to be:
import Data.ListTrie.Patricia.Map as P
import qualified Data.Map as Map
a :: P.TrieMap Map.Map Char Int
a = P.singleton "harry" 99
On Tue, Dec 20, 2011 at 1:07 AM, Stephen Tetley
Hi Matthew
You'll have to give `a` a concrete type, as `singleton` is overloaded, GHC cannot infer a type.
The TrieMap type is quite complicated as it allows different representations of (finite) Maps within it. There are three different internal maps you can use (the three pre-defined instances of the Map class - Data.Map, WrappedIntMap and AList) - I'd go for Data.Map as it will be faster than AList and I think you are using Char for key so you can't use an IntMap.
I don't have the package `list-tries` installed but I'd guess at one of these two for the concrete type signature.
Assuming you have imported Data.Map as
import qualified Data.Map as Map
(Probably this...) a :: TrieMap Map.Map [Char] Int
(Possibly this...) a :: TrieMap (Map.Map Char Int) [Char] Int