[Haskell-cafe] Data.EnumMap ?

Andres Löh andres.loeh at gmail.com
Tue Mar 31 17:53:18 UTC 2015


Hi.

Independently of your proposal, there already is
https://hackage.haskell.org/package/EnumMap

Cheers,
  Andres

On Tue, Mar 31, 2015 at 7:42 PM, Johannes Waldmann
<waldmann at imn.htwk-leipzig.de> wrote:
> Dear Cafe,
>
> in containers, we have Data.IntMap/IntSet .
> Because of the underlying implementation (patricia trees),
> keys/elements indeed have to be Int (we need their bits).
>
> This is a conflict with type-safety: I try to avoid Int,
> and use some  newtype T = T Int  instead.
> E.g., I want to distinguish several different indices
> for the same structure, like row and column numbers
> in (sparse) matrices, or vertices in bipartite graphs.
>
> So, I made these trivial wrappers EnumMap and EnumSet:
> https://github.com/jwaldmann/satchmo-solver/tree/master/src/Data
>
> Is this reasonable (do from/toEnum really have zero cost)?
> Would this be a useful addition to containers?
>
> - J.W.
>
>
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