eq

Leibnizian equality

http://github.com/ekmett/eq/

Version on this page:4.2.1
LTS Haskell 23.19:4.3@rev:1
Stackage Nightly 2025-04-30:4.3@rev:1
Latest on Hackage:4.3@rev:1

See all snapshots eq appears in

BSD-3-Clause licensed by Edward A. Kmett
Maintained by Edward A. Kmett
This version can be pinned in stack with:eq-4.2.1@sha256:b6a5dfa242b33820cd65232552a6d4d157897976f6e7682368e4e78b67f2a051,1422

Module documentation for 4.2.1

eq

Hackage Build Status

This package provides a data type that witnesses equality between two types using Leibnizian equality.

It includes a refinement to the notion of Leibnizian equality by Oleg Kiselyov that permits it to refine equality using the injectively of type constructors via type families.

Contact Information

Contributions and bug reports are welcome!

Please feel free to contact me through github or on the #haskell IRC channel on irc.freenode.net.

-Edward Kmett

Changes

4.2.1 [2020.10.01]

  • Allow building with GHC 9.0.

4.2 [2018.04.24]

  • Make lower, lower2, and lower3 in Data.Eq.Type poly-kinded.
  • Introduce the Data.Eq.Type.Hetero module, which exposes (:==), a heterogeneously kinded version of (:=). This module is only available on GHC 8.2 and later.

4.1

  • Add TestEquality and TestCoercion instances for (:=).
  • Add fromLeibniz and toLeibniz functions for converting between (:~:) (from Data.Type.Equality) and (:=).
  • Add a reprLeibniz function to convert (:=) to a Coercion (i.e., representational equality).
  • Make (:=) a newtype.
  • We can remove the Trustworthy claim and infer as Safe on modern GHCs.

4.0.2

  • Made := kind polymorphic.

4.0.1

  • Provided an explicit nominal RoleAnnotation.

4.0

  • Updated to work with semigroupoids 4.0

3.1.1

  • Claim to be Trustworthy

3.1

  • Disabled observing injectivity through TypeFamilies for GHC >= 7.6

3.0.1

  • Updated build system
  • Removed my personal intra-package dependency upper bounds
  • Added README and CHANGELOG