-- | -- Module : Data.Vector.Fusion.Stream.Size -- Copyright : (c) Roman Leshchinskiy 2008-2010 -- License : BSD-style -- -- Maintainer : Roman Leshchinskiy <rl@cse.unsw.edu.au> -- Stability : experimental -- Portability : portable -- -- Size hints for streams. -- module Data.Vector.Fusion.Stream.Size ( Size(..), smaller, larger, toMax, upperBound ) where import Data.Vector.Fusion.Util ( delay_inline ) -- | Size hint data Size = Exact Int -- ^ Exact size | Max Int -- ^ Upper bound on the size | Unknown -- ^ Unknown size deriving( Eq, Show ) instance Num Size where Exact m + Exact n = Exact (m+n) Exact m + Max n = Max (m+n) Max m + Exact n = Max (m+n) Max m + Max n = Max (m+n) _ + _ = Unknown Exact m - Exact n = Exact (m-n) Exact m - Max n = Max m Max m - Exact n = Max (m-n) Max m - Max n = Max m Max m - Unknown = Max m _ - _ = Unknown fromInteger n = Exact (fromInteger n) -- | Minimum of two size hints smaller :: Size -> Size -> Size {-# INLINE smaller #-} smaller (Exact m) (Exact n) = Exact (delay_inline min m n) smaller (Exact m) (Max n) = Max (delay_inline min m n) smaller (Exact m) Unknown = Max m smaller (Max m) (Exact n) = Max (delay_inline min m n) smaller (Max m) (Max n) = Max (delay_inline min m n) smaller (Max m) Unknown = Max m smaller Unknown (Exact n) = Max n smaller Unknown (Max n) = Max n smaller Unknown Unknown = Unknown -- | Maximum of two size hints larger :: Size -> Size -> Size {-# INLINE larger #-} larger (Exact m) (Exact n) = Exact (delay_inline max m n) larger (Exact m) (Max n) | m >= n = Exact m | otherwise = Max n larger (Max m) (Exact n) | n >= m = Exact n | otherwise = Max m larger (Max m) (Max n) = Max (delay_inline max m n) larger _ _ = Unknown -- | Convert a size hint to an upper bound toMax :: Size -> Size toMax (Exact n) = Max n toMax (Max n) = Max n toMax Unknown = Unknown -- | Compute the minimum size from a size hint lowerBound :: Size -> Int lowerBound (Exact n) = n lowerBound _ = 0 -- | Compute the maximum size from a size hint if possible upperBound :: Size -> Maybe Int upperBound (Exact n) = Just n upperBound (Max n) = Just n upperBound Unknown = Nothing