Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
222 views
in Technique[技术] by (71.8m points)

Map Function using list implementation haskell

Is there a way to write an implementation of the Haskell map function using list implementation?

I keep getting an error and I do not think I am on the right track. This is what I have:

map' :: (a -> b) -> [a] -> [b]
map' _ [] = []
map' xs ys = [ (x, y) | x <- xs | y <- ys ]

Any help or link that will guide me in the right direction would be much appreciated.

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)

I believe you mean "comprehension", instead of "implementation".

Either way, this would work:

map' f as = [f a | a <- as]
map' (* 2) [1..5]

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...