| Copyright | (C) 2016 Edward Kmett and Eric Mertens |
|---|---|
| License | BSD-style (see the file LICENSE) |
| Maintainer | Edward Kmett <ekmett@gmail.com> |
| Stability | experimental |
| Portability | non-portable |
| Safe Haskell | Trustworthy |
| Language | Haskell2010 |
Control.Lens.Internal.Coerce
Description
Synopsis
- coerce :: forall (k :: RuntimeRep) (a :: TYPE k) (b :: TYPE k). Coercible a b => a -> b
- coerce' :: forall a b. Coercible a b => b -> a
- (#..) :: (Profunctor p, Coercible c b) => (b -> c) -> p a b -> p a c
Documentation
coerce :: forall (k :: RuntimeRep) (a :: TYPE k) (b :: TYPE k). Coercible a b => a -> b #
The function coerce allows you to safely convert between values of
types that have the same representation with no run-time overhead. In the
simplest case you can use it instead of a newtype constructor, to go from
the newtype's concrete type to the abstract type. But it also works in
more complicated settings, e.g. converting a list of newtypes to a list of
concrete types.
This function is runtime-representation polymorphic, but the
RuntimeRep type argument is marked as Inferred, meaning
that it is not available for visible type application. This means
the typechecker will accept coerce @Int @Age 42.
(#..) :: (Profunctor p, Coercible c b) => (b -> c) -> p a b -> p a c #