vec: Vec: length-indexed (sized) list

[ bsd3, data, dependent-types, library ] [ Propose Tags ]

This package provides length-indexed (sized) lists, also known as vectors.

data Vec n a where
    VNil  :: Vec 'Nat.Z a
    (:::) :: a -> Vec n a -> Vec ('Nat.S n) a

The functions are implemented in four flavours:

As best approach depends on the application, vec doesn't do any magic transformation. Benchmark your code.

This package uses fin, i.e. not GHC.TypeLits, for indexes.

See Hasochism: the pleasure and pain of dependently typed haskell programming by Sam Lindley and Conor McBride for answers to how and why. Read APLicative Programming with Naperian Functors by Jeremy Gibbons for (not so) different ones.

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Versions [faq] 0, 0.1, 0.1.1,, 0.2, 0.3
Change log
Dependencies adjunctions (==4.4.*), base (>=4.7 && <4.13), base-compat (>=0.9.3 && <0.11), deepseq (>= && <1.5), distributive (>=0.5.3 && <0.7), fin (>=0.0.2 && <0.1), hashable (>= && <1.4), lens (>=4.16 && <4.18), semigroupoids (>=5.2.2 && <5.4), semigroups (>=0.18.4 && <0.20), transformers (>= && <0.6) [details]
License BSD-3-Clause
Copyright (c) 2017 Oleg Grenrus
Author Oleg Grenrus <>
Maintainer Oleg.Grenrus <>
Revised Revision 1 made by phadej at 2019-05-23T09:20:04Z
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Source repo head: git clone
Uploaded by phadej at 2019-04-25T17:47:25Z
Distributions LTSHaskell:0.1.1, NixOS:0.3, Stackage:0.1.1
Downloads 2944 total (239 in the last 30 days)
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Status Hackage Matrix CI
Docs available [build log]
Last success reported on 2019-04-25 [all 1 reports]


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