Haskell语言学习笔记（91）Comprehension Extensions

Comprehension Extensions

关于解析式的相关语言扩展。

ParallelListComp

Prelude> :set -XParallelListComp
Prelude> [(w,x,y,z) | w <- [1..3], x <- [2..4] | y <- [3..5], z <- [4..6]]
[(1,2,3,4),(1,3,3,5),(1,4,3,6),(2,2,4,4),(2,3,4,5),(2,4,4,6),(3,2,5,4),(3,3,5,5),(3,4,5,6)]
Prelude> [(w,x,y,z) | ((w,x),(y,z)) <- zip [(w,x) | w <- [1..3], x <- [2..4]] [(y,z) | y <- [3..5], z <- [4..6]]]
[(1,2,3,4),(1,3,3,5),(1,4,3,6),(2,2,4,4),(2,3,4,5),(2,4,4,6),(3,2,5,4),(3,3,5,5),(3,4,5,6)]