HList: Heterogeneous lists

[ data, library, mit ] [ Propose Tags ]

HList provides many operations to create and manipulate heterogenous lists (HLists) whose length and element types are known at compile-time. HLists are used to implement

  • records

  • variants

  • type-indexed products (TIP)

  • type-indexed co-products (TIC)

  • keyword arguments

User code should import Data.HList or Data.HList.CommonMain for a slightly more limited scope

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  • Data
    • Data.HList
      • Data.HList.CommonMain
      • Data.HList.Data
      • Data.HList.FakePrelude
      • Data.HList.HArray
      • Data.HList.HCurry
      • Data.HList.HList
      • Data.HList.HListPrelude
      • Data.HList.HOccurs
      • Data.HList.HSort
      • Data.HList.HTypeIndexed
      • Data.HList.HZip
      • Data.HList.Keyword
      • Data.HList.Label3
      • Data.HList.Label5
      • Data.HList.Label6
      • Data.HList.Labelable
      • Data.HList.MakeLabels
      • Data.HList.Record
      • Data.HList.RecordPuns
      • Data.HList.RecordU
      • Data.HList.TIC
      • Data.HList.TIP
      • Data.HList.TIPtuple
      • Data.HList.TypeEqO
      • Data.HList.Variant


Manual Flags


use Data.Type.Equality.== to define the instance of HEq instead of overlapping instances (in Data.HList.TypeEqO) (needs ghc >= 7.8)

This version does not allow `HEq x [x] f` to lead to f ~ False, unlike the version with overlapping instances. See https://ghc.haskell.org/trac/ghc/ticket/9918


Use -f <flag> to enable a flag, or -f -<flag> to disable that flag. More info


Note: This package has metadata revisions in the cabal description newer than included in the tarball. To unpack the package including the revisions, use 'cabal get'.

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For package maintainers and hackage trustees


Versions [RSS] 0.1, 0.1.1, 0.2, 0.2.1, 0.2.2, 0.2.3, 0.3.0,,,,,,,,,,,,
Change log ChangeLog
Dependencies array, base (>=4.6 && <4.9), base-orphans (>=0.3.3), ghc-prim, mtl, profunctors, tagged, template-haskell [details]
License MIT
Author 2004 Oleg Kiselyov (FNMOC, Monterey), Ralf Laemmel (CWI/VU, Amsterdam), Keean Schupke (London)
Maintainer oleg@pobox.com
Revised Revision 1 made by HerbertValerioRiedel at 2019-05-31T22:27:21Z
Category Data
Source repo head: darcs get http://code.haskell.org/HList
Uploaded by AdamVogt at 2015-12-22T23:25:15Z
Reverse Dependencies 25 direct, 31 indirect [details]
Downloads 20208 total (67 in the last 30 days)
Rating 2.0 (votes: 1) [estimated by Bayesian average]
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Readme for HList-

[back to package description]
(C) 2004--2010, Oleg Kiselyov, Ralf Laemmel, Keean Schupke

	Justin Bailey, Brian Bloniarz, Gwern Branwen, Einar Karttunen,
	and Adam Vogt

The HList library and samples


Getting the code

> darcs get http://code.haskell.org/HList


Pushing changes

You need an account at code.haskell.org

> cd HList
> darcs pull user@code.haskell.org:/srv/darcs/HList
> darcs record
> darcs push


This distribution covers all essential issues discussed in the HList paper,
though the implementation has been adapted to ghc features implemented
after the paper's writing.

Additional examples and HList operations are provided.
The code from the database section of the HList paper is not included
since doing so would have implied inclusion of substantial packages,
namely the underlying infrastructure for database access library.

You can get HList from Hackage or from Darcs:

$ cabal update && cabal install HList


$ darcs get --partial http://code.haskell.org/HList/
$ cd HList; cabal install

The code works --- within the limits exercised in the source files ---
for GHC-7.6 and GHC-7.8 and GHC-7.10. Older compilers are not supported.

One may run "cabal test" to check the distribution.

See ChangeLog for updates.