reflection: Reifies arbitrary terms into types that can be reflected back into terms

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

This package addresses the configuration problem which is propagating configurations that are available at run-time, allowing multiple configurations to coexist without resorting to mutable global variables or System.IO.Unsafe.unsafePerformIO.

That package is an implementation of the ideas presented in the paper "Functional Pearl: Implicit Configurations" by Oleg Kiselyov and Chung-chieh Shan (original paper). However, the API has been streamlined to improve performance.

Austin Seipp's tutorial Reflecting values to types and back provides a summary of the approach taken by this library, along with more motivating examples.

[Skip to Readme]
Versions [faq] 0.0.0, 0.1.0, 0.1.1, 0.2.0, 0.3.0, 0.3.1, 0.3.2, 0.3.3, 0.3.5, 0.4.0,,, 0.4.1,, 0.5,, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.1.1, 1.1.2, 1.1.3, 1.1.4, 1.1.5,, 1.1.6, 1.1.7,, 1.3, 1.3.1, 1.3.2, 1.4, 1.5.1,,, 1.5.2,, 2, 2.1, 2.1.1,, 2.1.2, 2.1.3, 2.1.4
Change log CHANGELOG.markdown
Dependencies base (>=2 && <5), semigroups (>=0.11 && <0.20), tagged (>=0.4.4 && <1), template-haskell [details]
License BSD-3-Clause
Copyright 2009-2013 Edward A. Kmett, 2012 Elliott Hird, 2004 Oleg Kiselyov and Chung-chieh Shan
Author Edward A. Kmett, Elliott Hird, Oleg Kiselyov and Chung-chieh Shan
Maintainer Edward A. Kmett <>
Revised Revision 1 made by ryanglscott at Fri May 10 14:27:03 UTC 2019
Category Data, Reflection, Dependent Types
Home page
Bug tracker
Source repo head: git clone git://
Uploaded by ryanglscott at Tue Jul 3 00:07:57 UTC 2018
Distributions Arch:2.1.4, Debian:2.1.4, Fedora:2.1.4, FreeBSD:2, LTSHaskell:2.1.4, NixOS:2.1.4, Stackage:2.1.4, openSUSE:2.1.4
Downloads 161474 total (635 in the last 30 days)
Rating 2.25 (votes: 2) [estimated by rule of succession]
Your Rating
  • λ
  • λ
  • λ
Status Hackage Matrix CI
Docs available [build log]
Last success reported on 2018-07-03 [all 1 reports]





If you enable this flag, we use a more portable much much slower implementation. Moreover, the Given API is broken, so this is currently an unsupported configuration. If you feel the need to turn on this flag for any reason, please email the maintainer!


You can disable the use of the template-haskell package using -f-template-haskell.

Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.


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'.

Maintainer's Corner

For package maintainers and hackage trustees

Readme for reflection-2.1.4

[back to package description]


Hackage Build Status

This package provides an implementation of the ideas presented in Functional Pearl: Implicit Configurations by Oleg Kiselyov and Chung-Chieh Shan. However, the API has been implemented in a much more efficient manner.

Contact Information

Contributions and bug reports are welcome!

Please feel free to contact me through github or on the #haskell IRC channel on

-Edward Kmett