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The map function works fine on really easy functions that take no arguments like *7 to every element in a list of Ints.

But say I made a custom function that takes a Char, String and Int and then returns a Char and I wanted to apply this function to a list of Chars i.e. a String to get a String back after applying the other function to each Char? When I try this all I get is error messages?

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  • You mean something like this: map (\x -> f x "string" 10) "another string" ? Commented Oct 13, 2013 at 12:17
  • What is the expected result of applying your function to a single Char? Commented Oct 13, 2013 at 12:18
  • map doesn't work on functions that take no arguments, but on functions that take one argument. The type of map is: map::(a -> b) -> [a] -> [b]. (a -> b) is a function that takes a value of type a to return another of type b. Commented Oct 13, 2013 at 12:19
  • @S.R.I I don't care if it's 0 or 1 argument, I know what it does! All I want to know is how I can map a function that takes many arguments to a list. Commented Oct 13, 2013 at 13:00
  • @Eddie, can you refine your question, then? In particular, answer n.m's question - or IOW, can you take partial function application? Commented Oct 13, 2013 at 13:02

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Put your Char argument to the last position:

foo :: String -> Int -> Char -> Char
foo str num c = c

bar = map (foo str num)

But we really need some more information from your side to help you better. Can you add the code you tried to write to your question?

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