filterByList Core comparison

elegant.core.txt

[1 of 1] Compiling Elegant          ( elegant.hs, elegant.o )

==================== Tidy Core ====================
Result size of Tidy Core = {terms: 20, types: 32, coercions: 0}

Elegant.filterByList1
  :: forall a_b. GHC.Types.Bool -> a_b -> [a_b] -> [a_b]
[GblId,
 Arity=3,
 Caf=NoCafRefs,
 Unf=Unf{Src=<vanilla>, TopLvl=True, Arity=3, Value=True,
         ConLike=True, WorkFree=True, Expandable=True,
         Guidance=ALWAYS_IF(unsat_ok=True,boring_ok=True)}]
Elegant.filterByList1 =
  \ (@ a_b)
    (x_agM :: GHC.Types.Bool)
    (y_agN :: a_b)
    (r_agO :: [a_b]) ->
    case x_agM of _ {
      GHC.Types.False -> r_agO;
      GHC.Types.True -> GHC.Types.: @ a_b y_agN r_agO
    }

Elegant.filterByList
  :: forall a_aeG. [GHC.Types.Bool] -> [a_aeG] -> [a_aeG]
[GblId,
 Arity=2,
 Caf=NoCafRefs,
 Str=DmdType SL,
 Unf=Unf{Src=<vanilla>, TopLvl=True, Arity=2, Value=True,
         ConLike=True, WorkFree=True, Expandable=True,
         Guidance=IF_ARGS [0 0] 50 0}]
Elegant.filterByList =
  \ (@ a_b) (ps_aeI :: [GHC.Types.Bool]) (as_aeJ :: [a_b]) ->
    GHC.List.foldr2
      @ GHC.Types.Bool
      @ a_b
      @ [a_b]
      (Elegant.filterByList1 @ a_b)
      (GHC.Types.[] @ a_b)
      ps_aeI
      as_aeJ

elegant.hs

module Main where

filterByList :: [Bool] -> [a] -> [a]
filterByList ps as = map snd . filter fst $ zip ps as

main :: IO ()
main = print . length $ filterByList (cycle [True, False]) [1..100000]

longhand.core.txt

[1 of 1] Compiling Longhand         ( longhand.hs, longhand.o )

==================== Tidy Core ====================
Result size of Tidy Core = {terms: 24, types: 28, coercions: 0}

Rec {
Longhand.filterByList [Occ=LoopBreaker]
  :: forall a_aeG. [GHC.Types.Bool] -> [a_aeG] -> [a_aeG]
[GblId, Arity=2, Caf=NoCafRefs, Str=DmdType SL]
Longhand.filterByList =
  \ (@ a_b) (ds_deQ :: [GHC.Types.Bool]) (ds1_deR :: [a_b]) ->
    case ds_deQ of _ {
      [] -> GHC.Types.[] @ a_b;
      : ipv_sfa ipv1_sfb ->
        case ds1_deR of _ {
          [] -> GHC.Types.[] @ a_b;
          : ipv2_sfe ipv3_sff ->
            case ipv_sfa of _ {
              GHC.Types.False -> Longhand.filterByList @ a_b ipv1_sfb ipv3_sff;
              GHC.Types.True ->
                GHC.Types.:
                  @ a_b ipv2_sfe (Longhand.filterByList @ a_b ipv1_sfb ipv3_sff)
            }
        }
    }
end Rec }

longhand.hs

module Main where

filterByList :: [Bool] -> [a] -> [a]
filterByList        []     _   = []
filterByList        _      []  = []
filterByList (True :ps) (a:as) = a : filterByList ps as
filterByList (False:ps) (_:as) =     filterByList ps as

main :: IO ()
main = print . length $ filterByList (cycle [True, False]) [1..100000]

shell.txt

bissbook:mapfiltbench bisserlis$ ghc -O2 -ddump-simpl longhand.hs > longhand.core.txt
bissbook:mapfiltbench bisserlis$ ghc -O2 -ddump-simpl elegant.hs > elegant.core.txt
bissbook:mapfiltbench bisserlis$ time ./longhand
50000

real	0m0.069s
user	0m0.004s
sys	0m0.002s
bissbook:mapfiltbench bisserlis$ time ./elegant
50000

real	0m0.012s
user	0m0.009s
sys	0m0.002s