License | BSD-style (see the LICENSE file in the distribution) |
---|---|
Maintainer | libraries@haskell.org |
Stability | experimental |
Portability | not portable |
Safe Haskell | None |
Language | Haskell2010 |
Data.Type.Coercion
Description
Definition of representational equality (Coercion
).
Since: 4.7.0.0
Documentation
data Coercion a b where Source #
Representational equality. If Coercion a b
is inhabited by some terminating
value, then the type a
has the same underlying representation as the type b
.
To use this equality in practice, pattern-match on the Coercion a b
to get out
the Coercible a b
instance, and then use coerce
to apply it.
Since: 4.7.0.0
Instances
Category k (Coercion k) Source # | |
TestCoercion k (Coercion k a) Source # | |
Coercible k a b => Bounded (Coercion k a b) Source # | |
Coercible k a b => Enum (Coercion k a b) Source # | |
Eq (Coercion k a b) Source # | |
(Coercible * a b, Data a, Data b) => Data (Coercion * a b) Source # | |
Ord (Coercion k a b) Source # | |
Coercible k a b => Read (Coercion k a b) Source # | |
Show (Coercion k a b) Source # | |
coerceWith :: Coercion a b -> a -> b Source #
Type-safe cast, using representational equality
trans :: Coercion a b -> Coercion b c -> Coercion a c Source #
Transitivity of representational equality
repr :: (a :~: b) -> Coercion a b Source #
Convert propositional (nominal) equality to representational equality
class TestCoercion f where Source #
This class contains types where you can learn the equality of two types from information contained in terms. Typically, only singleton types should inhabit this class.
Minimal complete definition
Methods
testCoercion :: f a -> f b -> Maybe (Coercion a b) Source #
Conditionally prove the representational equality of a
and b
.
Instances
TestCoercion k (Coercion k a) Source # | |
TestCoercion k ((:~:) k a) Source # | |