CODEWITHSUNDEEP
haskellinteger
user2057017
user2057017

Reputation: 5

detecting Integers in Haskell

I'm trying to use Haskell (which I am completely new too) and Every time I attempt to compile this using ghci I get Not in scope: 'isNumber', what am I doing wrong?

digits :: [a] -> Bool
digits a = digits a True


digits1 :: [a] -> Bool -> Bool
digits1 [] False      = False           
digits1 [] True       = True            
digits1 (l:ls) True   = digits ls isNumber l
digits1 (l:ls) False  = False

Upvotes: 0

Views: 620

Answers (1)

sepp2k
sepp2k

Reputation: 370152

You get that error message because isNumber is defined in the Data.Char module, which you didn't import it. Importing it will fix that error.

That's not your only problem though. One other problem is that digits ls isNumber l is calling digits with four arguments, but you've defined digits to only take one argument.

Similarly the call digits a True calls digits with two arguments - same problem. You probably meant to write digits1 a True here, as digits1 does take two arguments.

Lastly both digits and digits1 are defined to take arbitrary lists as arguments, but you seem to want to call isNumber on the list's elements. Since isNumber is a function that only works on Chars - not arbitrary values - you should probably take a list of Chars (i.e. a String) instead.

Upvotes: 7

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