Function of $ in the given Haskell line

Question

Can anybody tell me the function of $ in following Haskell line. $$ if for the last line but the function of $?

  concat $ replicate 3 "12345"

http://hackage.haskell.org/package/base-4.8.1.0/docs/Prelude.html#v:-36- — ApproachingDarknessFish, Nov 13 '15 at 18:03
Also https://www.haskell.org/hoogle/?hoogle=%24 and http://hayoo.fh-wedel.de/?query=%24 — kosmikus, Nov 13 '15 at 18:24
The marked duplicate actually has more information than you asked for, but lots of good answers. — dfeuer, Nov 13 '15 at 18:25

score 5 · Answer 1 · answered Nov 13 '15 at 18:02

$ is just a low precedence version of function application, i.e. a $ b is the same as a b.

It is commonly used to remove the need for parentheses, e.g.:

concat $ replicate 3 "12345"

is the same as:

concat (replicate 3 "12345")

Also, instead of having to write:

putStrLn ("hello " ++ name ++ "!")

you'll often see:

putStrLn $ "hello " ++ name ++ "!"

1 Answers1