On Thu, Oct 25, 2007 at 09:52:27AM -0700, Don Stewart wrote:
dons:
claus.reinke:
From my point of view, the difference between 0b10111011 and (bin[1,0,1,1,1,0,1,1]) is 22-10 that is 12 characters.
how about using ghc's new overloaded strings for this?
"10111011"::Binary
there used to be a way to link to ghc head's docs, but i can't find it right now. the test is
http://darcs.haskell.org/testsuite/tests/ghc-regress/typecheck/should_compil...
and the xml docs would be
http://darcs.haskell.org/ghc/docs/users_guide/glasgow_exts.xml
Why not use a Num instance for Binary, with fromInteger :: Integer -> a, Yielding,
10111011 :: Binary
Overloaded numeric literals seem better here than strings :)
Something like this:
import Data.List import Data.Bits
newtype Binary = Binary Integer deriving (Eq, Show)
instance Num Binary where fromInteger n = Binary . roll . map (read.return) . show $ n where roll = foldl' unstep 0
unstep a 1 = a `shiftL` 1 .|. fromIntegral 1 unstep a 0 = a `shiftL` 1 unstep a _ = error "Invalid character in binary literal"
Yielding,
*A> 0 :: Binary Binary 0
*A> 101 :: Binary Binary 5
*A> 1111 :: Binary Binary 15
*A> 1010101011010111 :: Binary Binary 43735
*A> 42 :: Binary Binary *** Exception: Invalid character in binary literal
This would have some decidedly weird consequences fromIntegral (6::Int) :: Binary Binary *** Exception: Invalid character in binary literal and that constant 6 can be somewhere far removed from the actual binary cast. also, fromInteger (toInteger x + toInteger y ) :: Binary /= x + y all sorts of oddness will result. John -- John Meacham - ⑆repetae.net⑆john⑈