Data.Proxy

Tagged values

data Proxy p

Constructors

Proxy

Instances

Monad Proxy

Functor Proxy

Typeable1 Proxy

Applicative Proxy

Foldable Proxy

Traversable Proxy

Bounded (Proxy s)

Enum (Proxy s)

Eq (Proxy p)

Data p => Data (Proxy p)

Ord (Proxy p)

Read (Proxy p)

Show (Proxy p)

Ix (Proxy s)

Monoid (Proxy s)

Default (Proxy s)

Semigroup (Proxy s)

reproxy :: Proxy s -> Proxy t

Some times you need to change the proxy you have lying around. Idiomatic usage is to make a new combinator for the relationship between the proxies that you want to enforce, and define that combinator using reproxy.

 data Succ n
 reproxySucc :: Proxy n -> Proxy (Succ n)
 reproxySucc = reproxy

asProxyTypeOf :: a -> Proxy a -> a

asProxyTypeOf is a type-restricted version of const. It is usually used as an infix operator, and its typing forces its first argument (which is usually overloaded) to have the same type as the tag of the second.

Conversion

proxy :: Tagged s a -> Proxy s -> a

Convert from a Tagged representation to a representation based on a Proxy.

unproxy :: (Proxy s -> a) -> Tagged s a

Convert from a representation based on a Proxy to a Tagged representation.