Control.Lens.Internal.Coerce

lens-4.15.1: Lenses, Folds and Traversals

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 | Haskell98

Control.Lens.Internal.Coerce

Description

This module provides a shim around `coerce` that defaults to `unsafeCoerce` on GHC < 7.8

Synopsis

- coerce :: Coercible * a b => a -> b
- coerce' :: forall a b. Coercible a b => b -> a

# Documentation

coerce :: 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.

coerce' :: forall a b. Coercible a b => b -> a #