[Gtk2hs-commit] (main branch): glib: add toFlags': like toFlags but works doesn't fail when we haven't defined toEnum for a bit

[Axel S. <A....@ke...>]

Mon Nov  5 07:06:31 PST 2007  Peter Gavin <pg...@gm...>
  * glib: add toFlags': like toFlags but works doesn't fail when we haven't defined toEnum for a bit
  This is needed for a few reasons, the most important of which is for forward compatibility.
  If a newer version of the upstream package defines a new flag for a flag type, we shouldn't
  fail just because we don't recognize it. This version allows overlapping flags, for example, given:
  
  data OpenFlags = Read | Write | ReadWrite
  instance Flags OpenFlags
  instance Enum OpenFlags where ...
  
  If ReadWrite is equivalent to [ Read, Write ] in C land, then it will be in Haskell land as well.
  

    hunk ./glib/System/Glib/Flags.hs 30
    -  toFlags
    +  toFlags,
    +  toFlags'
    hunk ./glib/System/Glib/Flags.hs 34
    -import Data.Bits ((.|.), testBit, shiftL, shiftR)
    +import Data.Bits ((.|.), (.&.), testBit, shiftL, shiftR)
    +import Data.Maybe (catMaybes)
    hunk ./glib/System/Glib/Flags.hs 56
    +-- * Unlike 'toFlags', this function ignores bits set in the passed
    +--   'Int' that do not correspond to a flag.
    +toFlags' :: Flags a => Int -> [a]
    +toFlags' n = catMaybes [ if n .&. fromEnum flag == fromEnum flag
    +                            then Just flag
    +                            else Nothing
    +                       | flag <- [ minBound .. maxBound ] ]
    +