Infix operator

From HaskellWiki
Revision as of 23:45, 25 June 2021 by Atravers (talk | contribs) (Various minor changes)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to navigation Jump to search


Functions in Haskell are usually called using prefix notation, or the function name followed by its arguments. However, some functions e.g. addition are called using infix notation - putting the function name between its two arguments:

 Prelude> 17 + 25

Using infix functions with prefix notation

Putting parentheses around an infix operator converts it into a prefix function:

 Prelude> (+) 1 2
 Prelude> (*) 3 4

Using prefix functions with infix notation

Putting `-marks around a prefix function allows us to use it like an infix function:

 Prelude> let concatPrint x y = putStrLn $ (++) x y
 Prelude> concatPrint "a" "b"
 Prelude> "a" `concatPrint` "b"

Note that you can only normally do this with a function that takes two arguments. Actually, for a function taking more than two arguments, you can do it but it's not nearly as nice (note the need for extra parentheses):

Prelude> foldl (+) 0 [1..5]
Prelude> ((+) `foldl` 0) [1..5]

See also