Re: [Haskell-cafe] Key-Parametrized Lookup Table

First of all I'd like to thank everyone who participated in this discussion! Most approaches look very promising, especially the last is what I imagined, but were unable to write. Thanks for that, especially. I will try to solve my problem using these approaches and report back once I succeed or r

Re: [Haskell-cafe] Key-Parametrized Lookup Table

This is without class :-) {-# LANGUAGE TypeFamilies, ExistentialQuantification, FlexibleContexts #-} import Prelude hiding (lookup) import Data.Typeable type family Value a :: * data Assoc = forall a . (Typeable (Value a), Typeable a) => Assoc a (Value a) insert :: (Typeable (Value a), Typeable

Re: [Haskell-cafe] Key-Parametrized Lookup Table

Hello, I made some trial and error with ghci to make it happy. I'm not really sure this has the type safety you asked. {-# LANGUAGE TypeFamilies, ExistentialQuantification, FlexibleContexts #-} import Prelude hiding (lookup) import Data.Typeable class Typeable a => Key a where type Value a :

Re: [Haskell-cafe] Key-Parametrized Lookup Table

Alexander Foremny wrote: At first glance I noticed some problems with the vault library for my particular approach. Despite from being unique, Key values don't appear to carry any information like the Label I need. However, it might be possible to work around that. The more grave problem seems

Re: [Haskell-cafe] Key-Parametrized Lookup Table

Another option which allows you to define your own key type is the dependent-map[1] package. It requires implementing some classes for your key type that encode a proof that key equality entails equality of the type indices. If the documentation is insufficient feel free to ask me for more det

Re: [Haskell-cafe] Key-Parametrized Lookup Table

Would ixset or HiggsSet be suitable? http://hackage.haskell.org/package/ixset http://hackage.haskell.org/package/HiggsSet On Tue, Jul 31, 2012 at 12:56 PM, Alexander Foremny < alexanderfore...@gmail.com> wrote: > At first glance I noticed some prob

Re: [Haskell-cafe] Key-Parametrized Lookup Table

At first glance I noticed some problems with the vault library for my particular approach. Despite from being unique, Key values don't appear to carry any information like the Label I need. However, it might be possible to work around that. The more grave problem seems to be that a Key cannot be

Re: [Haskell-cafe] Key-Parametrized Lookup Table

Dear Michael, thank you very much for your quick and interesting response. This looks very much like what I want! Regards, Alexander Foremny 2012/7/31 Michael Snoyman : > On Tue, Jul 31, 2012 at 1:13 PM, Alexander Foremny > wrote: >> Hello list, >> >> I am currently thinking that a problem of m

Re: [Haskell-cafe] Key-Parametrized Lookup Table

On Tue, Jul 31, 2012 at 1:13 PM, Alexander Foremny wrote: > Hello list, > > I am currently thinking that a problem of mine would best be solved if > there was a Map-like data structure in which the value returned is > parametrized over the lookup type. > > I wonder is this makes sense and if such