| Copyright | (c) 2014 Patrick Bahr |
|---|---|
| License | BSD3 |
| Maintainer | Patrick Bahr <paba@di.ku.dk> |
| Stability | experimental |
| Portability | non-portable (GHC Extensions) |
| Safe Haskell | Safe |
| Language | Haskell98 |
Data.Comp.Projection
Description
This module provides a generic projection function pr for
arbitrary nested binary products.
Documentation
pr :: forall p q. p :< q => q -> p Source #
This function projects the component of type e out or the
compound value of type p.
type (:<) f g = Proj (ComprEmb (Elem f g)) f g infixl 5 Source #
The constraint e :< p expresses that e is a component of the
type p. That is, p is formed by binary products using the type
e. The occurrence of e must be unique. For example we have Int
:< (Bool,(Int,Bool)) but not Bool :< (Bool,(Int,Bool)).