[wxhaskell-users] type safe handling of flags

[Henning T. <le...@he...>]

I don't know whether I proposed it already ...

I wrote a package called enumset. It provides low-level bitsets like they 
are used by wxWidget. The definition is essentially:

newtype EnumSet storage index = EnumSet storage

E.g. with

data Style = Bold | Italic | Underlined  deriving (Enum)

the type (EnumSet Word32 Style) represents a subset of {Bold, Italic, 
Underlined} stored as a bitfield in a Word32.

http://hackage.haskell.org/packages/archive/enumset/0.0.4/doc/html/Data-EnumSet.html


The other modules can be used to manage bitfields where not individual 
bits must be processed, but there are groups of bits, where each group 
represents a value.