unpacked-containers-0: utils/Internal/StrictFold.hs

{-# LANGUAGE CPP #-}
#if !defined(TESTING) && __GLASGOW_HASKELL__ >= 703
{-# LANGUAGE Safe #-}
#endif

#include "containers.h"
{-# OPTIONS_HADDOCK hide #-}

module Internal.StrictFold (foldlStrict) where

-- | Same as regular 'Data.List.foldl'', but marked INLINE so that it is always
-- inlined. This allows further optimization of the call to f, which can be
-- optimized/specialised/inlined.

foldlStrict :: (a -> b -> a) -> a -> [b] -> a
foldlStrict f = go
  where
    go z []     = z
    go z (x:xs) = let z' = f z x in z' `seq` go z' xs
{-# INLINE foldlStrict #-}