Haskell Input & Passing Values to Functions

Question

putStrLn "Enter the Artist Name"
    art <- getLine
putStrLn "Enter the Number of CD's"
    num <- getLine

let test= buyItem currentStockBase art num
    printListIO (showcurrentList test)

the values i have to pass for buyItem is

buyItem currentStockBase "Akon" 20

but i want to send "Akon" to art and for 20 i want to send num

it gives me this error

ERROR file:.\Project2.hs:126 - Type error in application
*** Expression     : buyItem currentStockBase art num
*** Term           : num
*** Type           : [Char]
*** Does not match : Int

please help me

Do yourself a favor and look at book.realworldhaskell.org and learnyouahaskell.com. I bet it won't be as frustrating as getting stuck all the time and waiting for answers here. — stefaanv
– stefaanv, Commented Mar 18, 2010 at 11:58

dave4420 · Accepted Answer · 2010-03-18 14:27:59Z

5

num is a String. buyItem is expecting an Int. You need to convert the String into an Int, for example by using read.

buyItem currentStockBase art (read num)

Edit: String means [Char] --- hopefully this means the error message makes more sense to you now.

edited Mar 18, 2010 at 14:27

answered Mar 18, 2010 at 11:59

dave4420

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Jason Reich · Accepted Answer · 2010-03-18 11:59:15Z

2

Is it because num is a string? Try parsing it with read:

let test= buyItem currentStockBase art (read num)

answered Mar 18, 2010 at 11:59

Jason Reich

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