Portability | portable |
---|---|
Stability | provisional |
Maintainer | otakar.smrz mff.cuni.cz |
The Haskell analogy to the Encode module in Perl: http://search.cpan.org/dist/Encode/
Classes
Encodings are represented as distinct datatypes of the Encoding
class,
which defines two essential methods:
encode
- turning a list of 'internal code points' into a
String
, and decode
- converting the lists in the opposite direction.
Developing a new encoding means to write a new module with a structure similar to this:
module MyEncModule (MyEncType (..)) where import Encode data MyEncType = MyEncName | MyEncAlias deriving (Enum, Show) instanceEncoding
MyEncType whereencode
enc data = show data -- your choices ...decode
enc data = map (toEnum . fromEnum) data
Encode.Unicode.UTF8 is one concrete implementation that realizes and illustrates this template. Encode.Arabic.Buckwalter implements symmetric recoding using finite maps, and Encode.Arabic.ArabTeX makes use of monadic parsing and the PureFP library.
Types
The datatype introduced for the internal representation of Unicode code
points is currently defined as newtype
. The
shift to code points UPoint
= UPoint CSpaceUPoint
from characters Char
is intentional, as
Unicode support in Haskell is not yet fully implemented, and code points
are, anyway, different entities. Since the UPoint
type is an instance
of the Enum
class, the type's constructor and destructor functions are
available as toEnum
and fromEnum
, respectively.
The UPoint
datatype should be the transfer point on the way from one
encoding into another. It should not be the terminal stop, though. The
encode
method should be used systematically, and not show
, even if
it might temporarily produce somehow appealing results.