| Copyright | (c) The University of Glasgow 2001 |
|---|---|
| License | BSD-style (see the file libraries/base/LICENSE) |
| Maintainer | [email protected] |
| Stability | experimental |
| Portability | portable |
| Safe Haskell | Trustworthy |
| Language | Haskell2010 |
Data.Dynamic
Contents
Description
The Dynamic interface provides basic support for dynamic types.
Operations for injecting values of arbitrary type into a dynamically typed value, Dynamic, are provided, together with operations for converting dynamic values into a concrete (monomorphic) type.
The Dynamic type
A value of type Dynamic is an object encapsulated together with its type.
A Dynamic may only represent a monomorphic value; an attempt to
create a value of type Dynamic from a polymorphically-typed
expression will result in an ambiguity error (see toDyn).
Showing a value of type Dynamic returns a pretty-printed representation
of the object's type; useful for debugging.
Converting to and from Dynamic
toDyn :: Typeable a => a -> Dynamic Source #
Converts an arbitrary value into an object of type Dynamic.
The type of the object must be an instance of Typeable, which
ensures that only monomorphically-typed objects may be converted to
Dynamic. To convert a polymorphic object into Dynamic, give it
a monomorphic type signature. For example:
toDyn (id :: Int -> Int)
Arguments
| :: Typeable a | |
| => Dynamic | the dynamically-typed object |
| -> a | a default value |
| -> a | returns: the value of the first argument, if it has the correct type, otherwise the value of the second argument. |
Converts a Dynamic object back into an ordinary Haskell value of
the correct type. See also fromDynamic.
Applying functions of dynamic type
dynTypeRep :: Dynamic -> SomeTypeRep Source #