type-level-sets: Type-level sets (with value-level counterparts and various operations)

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This package provides type-level sets (no duplicates, sorted to provide a nomral form) via Set, with value-level counterparts. Described in the paper "Embedding effect systems in Haskell" by Dominic Orchard and Tomas Petricek http://www.cl.cam.ac.uk/~dao29/publ/haskell14-effects.pdf (Haskell Symposium, 2014)

Here is a brief example:

import Data.Type.Set

foo :: Set '["x" :-> Int, "z" :-> Int, "w" :-> Int]
foo = Ext ((Var :: (Var "x")) :-> 2) $
        Ext ((Var :: (Var "z")) :-> 4) $
          Ext ((Var :: (Var "w")) :-> 5) $
            Empty

bar :: Set '["y" :-> Int, "w" :-> Int]
bar = Ext ((Var :: (Var "y")) :-> 3) $
        Ext ((Var :: (Var "w")) :-> 1) $
          Empty

-- foobar :: Set '["w" :-> Int, "x" :-> Int, "y" :-> Int, "z" :-> Int]
foobar = foo `union` bar

The Set type for foobar here shows the normalised form (sorted with no duplicates). The type signatures is commented out as it can be infered. Running the example we get:

>>> foobar
[(Var :-> 1), (Var :-> 2), (Var :-> 3), (Var :-> 4)]

Thus, we see that the first value paired with the "w" variable is dropped.

Properties

Versions 0.5, 0.5, 0.6, 0.6.1, 0.7, 0.8.0.0, 0.8.5.0, 0.8.6.0, 0.8.7.0, 0.8.9.0
Change log None available
Dependencies base (<5), ghc-prim [details]
License BSD-3-Clause
Copyright 2013-14 University of Cambridge
Author Dominic Orchard
Maintainer Dominic Orchard
Category Type System, Data Structures
Source repo head: git clone https://github.com/dorchard/type-level-sets
Uploaded by DominicOrchard at 2014-09-11T14:46:21Z

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