module Examples.Simple.Sharing where

import qualified Prelude
import Feldspar
import Feldspar.Wrap
import Feldspar.Vector
import Feldspar.Compiler

-- | Examples on the optimization transformation 'sharing' (also called 'common subexpression elimination').

share1 :: Data Int32 -> Data Int32
share1 v = w + w where
    w = 2 * v

share2 :: Data Int32 -> Data Int32
share2 v = (2*v) + (2*v)

share3 :: Data Int32 -> Vector1 Int32
share3 v = indexed 10 $ const w where
    w = 2 * v + v

share4 :: Data Int32 -> Vector1 Int32
share4 v = indexed 10 $ const w where
    w = 2 * q + q where
     q = v + 1

share4' :: Data Int32 -> Data [Int32]
share4' = wrap share4

share5 :: Data Index -> Vector1 Index
share5 v = indexed 10 $ \ix -> w ix where
    w ix = 2 * v + ix

share5' :: Data Index -> Data [Index]
share5' = wrap share5

share6 :: Vector1 Int32 -> Vector1 Int32
share6 v = share (map (*2) v) $ \w -> zipWith (+) w w

save1 :: Vector1 Index -> Vector1 Index
save1 = map (*3) . save . reverse

save2 :: Data Index -> Data Index
save2 = (*3) . save . (+2)