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# Roles
**Update** (March, 2014): There is a draft paper describing roles, including much discussion of design decisions, [ here](http://www.cis.upenn.edu/~eir/papers/2014/coercible/coercible-ext.pdf).
The idea of *roles* comes from the paper [ Generative Type Abstraction and Type-level Computation](http://www.seas.upenn.edu/~sweirich/papers/popl163af-weirich.pdf), published at POPL 2011. The implementation of roles in GHC, however, is somewhat different than stated in that paper. This page focuses on the user-visible features of roles.
The idea of *roles* comes from the paper [ Generative Type Abstraction and Type-level Computation](http://www.seas.upenn.edu/~sweirich/papers/popl163af-weirich.pdf), published at POPL 2011. The implementation of roles in GHC, however, is somewhat different than stated in that paper. This page focuses on the user-visible features of roles. [RolesImplementation](roles-implementation) talks about the implementation in GHC. See also [ Richard's blog post about roles](http://typesandkinds.wordpress.com/2013/08/15/roles-a-new-feature-of-ghc/). (Note: some aspects of that blog post are out of date, as of December 17, 2013.)
See also
See also this email thread: [ More GND + role inference woes](http://www.haskell.org/pipermail/ghc-devs/2013-October/003003.html).
- Our ICFP 2014 paper [ Safe Coercions](http://www.cis.upenn.edu/~eir/papers/2014/coercible/coercible-ext.pdf), which gives lots of motivation and details, including the `Coercible` class.
- [Roles2](roles2) which identifies a difficulty with the design in the paper, and some possibilities for solving it.
- [RolesImplementation](roles-implementation) talks about the implementation in GHC.
- [ Richard's blog post about roles](http://typesandkinds.wordpress.com/2013/08/15/roles-a-new-feature-of-ghc/). (Note: some aspects of that blog post are out of date, as of December 17, 2013.)
- This email thread: [ More GND + role inference woes](http://www.haskell.org/pipermail/ghc-devs/2013-October/003003.html).
## The problem we wish to solve
......