CODEWITHSUNDEEP
haskellimportmodule
Mark Hildreth
Mark Hildreth

Reputation: 43111

How to import an exclamation point (or other operator) from Haskell module

Haskell has a Data.Map module which includes, among other functions, a ! function.

fromList [(5,'a'), (3,'b')] ! 1    Error: element not in the map
fromList [(5,'a'), (3,'b')] ! 5 == 'a'

While I can import other functions from the Data.Map module into my code...

import Data.Map(Map, keys, fromList)

...the following does NOT work...

import Data.Map(Map, keys, fromList, !)

I get the following error:

parse error on input `!'

What is the correct syntax to import items like !?

Upvotes: 20

Views: 2937

Answers (1)

Mark Hildreth
Mark Hildreth

Reputation: 43111

The correct answer is to wrap the function name (really, it's an operator: a special case of a function) in parentheses, like so...

import Data.Map(Map, keys, fromList, (!))

Upvotes: 31

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