| Safe Haskell | Safe |
|---|---|
| Language | Haskell98 |
Data.Proxy.Compat
Synopsis
- module Data.Proxy
- asProxyTypeOf :: a -> proxy a -> a
Documentation
module Data.Proxy
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.
>>>import Data.Word>>>:type asProxyTypeOf 123 (Proxy :: Proxy Word8)asProxyTypeOf 123 (Proxy :: Proxy Word8) :: Word8
Note the lower-case proxy in the definition. This allows any type
constructor with just one argument to be passed to the function, for example
we could also write
>>>import Data.Word>>>:type asProxyTypeOf 123 (Just (undefined :: Word8))asProxyTypeOf 123 (Just (undefined :: Word8)) :: Word8