小编Vũ *_* Tô的帖子

我在这里发现了一种"奇怪"的行为.我懂了:

{-# LANGUAGE BangPatterns #-}

import Data.List
import Control.Parallel
import Control.Parallel.Strategies

fib 0 = 1
fib 1 = 1
fib n = fib (n-1) + fib (n-2)

main =
  let xs = [ fib (20 + n `mod` 2) | n <- [0..1000] ]
              `using` test rseq
   in print (sum xs)

test :: Strategy a -> Strategy [a]
test strat xs = do
  parTraversable strat xs  -- case #1
  -- parList strat xs      -- case #2
  return xs

case #1 …