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|
-- |
-- Module : Data.Vector.Fusion.Bundle.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.Bundle.Size (
Size(..), clampedSubtract, smaller, larger, toMax, upperBound, lowerBound
) 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 = checkedAdd Exact m n
Exact m + Max n = checkedAdd Max m n
Max m + Exact n = checkedAdd Max m n
Max m + Max n = checkedAdd Max m n
_ + _ = Unknown
Exact m - Exact n = checkedSubtract Exact m n
Exact m - Max _ = Max m
Max m - Exact n = checkedSubtract Max m n
Max m - Max _ = Max m
Max m - Unknown = Max m
_ - _ = Unknown
fromInteger n = Exact (fromInteger n)
(*) = error "vector: internal error * for Bundle.size isn't defined"
abs = error "vector: internal error abs for Bundle.size isn't defined"
signum = error "vector: internal error signum for Bundle.size isn't defined"
{-# INLINE checkedAdd #-}
checkedAdd :: (Int -> Size) -> Int -> Int -> Size
checkedAdd con m n
-- Note: we assume m and n are >= 0.
| r < m || r < n =
error $ "Data.Vector.Fusion.Bundle.Size.checkedAdd: overflow: " ++ show r
| otherwise = con r
where
r = m + n
{-# INLINE checkedSubtract #-}
checkedSubtract :: (Int -> Size) -> Int -> Int -> Size
checkedSubtract con m n
| r < 0 =
error $ "Data.Vector.Fusion.Bundle.Size.checkedSubtract: underflow: " ++ show r
| otherwise = con r
where
r = m - n
-- | Subtract two sizes with clamping to 0, for drop-like things
{-# INLINE clampedSubtract #-}
clampedSubtract :: Size -> Size -> Size
clampedSubtract (Exact m) (Exact n) = Exact (max 0 (m - n))
clampedSubtract (Max m) (Exact n)
| m <= n = Exact 0
| otherwise = Max (m - n)
clampedSubtract (Exact m) (Max _) = Max m
clampedSubtract (Max m) (Max _) = Max m
clampedSubtract _ _ = Unknown
-- | 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
|
