dependent-map: Dependent finite maps (partial dependent products)

[ data, dependent-types, library ] [ Propose Tags ]

Provides a type called DMap which generalizes Data.Map.Map, allowing keys to specify the type of value that can be associated with them.


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Versions [faq] 0.1, 0.1.1, 0.1.1.1, 0.1.1.2, 0.1.1.3, 0.2.0.1, 0.2.1.0, 0.2.2.0, 0.2.3.0, 0.2.4.0, 0.3, 0.3.1.0, 0.4.0.0
Change log ChangeLog.md
Dependencies base (>=4.9 && <5), constraints-extras (>=0.2.3.0 && <0.4), containers (>=0.5.7.1 && <0.7), dependent-sum (>=0.6.1 && <0.8) [details]
License LicenseRef-OtherLicense
Author James Cook <mokus@deepbondi.net>
Maintainer Obsidian Systems, LLC <maintainer@obsidian.systems>
Category Data, Dependent Types
Home page https://github.com/obsidiansystems/dependent-map
Source repo head: git clone https://github.com/obsidiansystems/dependent-map
Uploaded by 3noch at 2020-03-27T02:06:15Z
Distributions Debian:0.2.4.0, LTSHaskell:0.2.4.0, NixOS:0.4.0.0, Stackage:0.2.4.0
Downloads 14840 total (320 in the last 30 days)
Rating 2.5 (votes: 3) [estimated by Bayesian average]
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Readme for dependent-map-0.4.0.0

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dependent-map Build Status Hackage

This library defines a dependently-typed finite map type. It is derived from Data.Map.Map in the containers package, but rather than (conceptually) storing pairs indexed by the first component, it stores DSums (from the dependent-sum package) indexed by tag. For example

{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE TypeFamilies #-}
module Example where

import Data.Constraint.Extras.TH (deriveArgDict)
import Data.Dependent.Map (DMap, fromList, singleton, union, unionWithKey)
import Data.Dependent.Sum ((==>))
import Data.Functor.Identity (Identity(..))
import Data.GADT.Compare.TH (deriveGCompare, deriveGEq)
import Data.GADT.Show.TH (deriveGShow)

data Tag a where
  StringKey :: Tag String
  IntKey    :: Tag Int
  DoubleKey :: Tag Double
deriveGEq ''Tag
deriveGCompare ''Tag
deriveGShow ''Tag
deriveArgDict ''Tag

x :: DMap Tag Identity
x = fromList [DoubleKey ==> pi, StringKey ==> "hello there"]

y :: DMap Tag Identity
y = singleton IntKey (Identity 42)

z :: DMap Tag Identity
z = y `union` fromList [DoubleKey ==> -1.1415926535897931]

addFoo :: Tag v -> Identity v -> Identity v -> Identity v
addFoo IntKey (Identity x) (Identity y) = Identity $ x + y
addFoo DoubleKey (Identity x) (Identity y) = Identity $ x + y
addFoo _ x _ = x

main :: IO ()
main = mapM_ print
  [ x, y, z
  , unionWithKey addFoo x z
  ]