CODEWITHSUNDEEP
haskell
brainuser5705
brainuser5705

Reputation: 31

Error when passing in negative number into Haskell function?

newcomer to Haskell here.

I have this function:

addNums num1 num2 =
             num1 + num2

when I try to run addNums 1 -2 with GHCi, it returns this error:

<interactive>:40:1: error:
* No instance for (Show (Integer -> Integer))
    arising from a use of `print'
    (maybe you haven't applied a function to enough arguments?)
* In a stmt of an interactive GHCi command: print it

I notice that in order for it to run as intended, I need to add parentheses: addNums 1 (-2). Why is that?

Upvotes: 1

Views: 396

Answers (1)

Fyodor Soikin
Fyodor Soikin

Reputation: 80754

The code you wrote is being parsed as (addNums 1) - 2, so the compiler takes the result of addNums 1, which is a function Integer -> Integer, and tries to subtract 2 from it.

For correct passing order, you need to add parentheses around the second parameter:

addNum 1 (-2)

Upvotes: 3

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