CODEWITHSUNDEEP
haskell
chowmean
chowmean

Reputation: 152

Getting parse error on input `=' error

import Data.Char (digitToInt)

let f [] = []
     f ('\n':',':a) = f ('\n' : a)  
     f (a:b) = a : f b

main :: IO ()

main = do
     ln<-getLine
     f ln
     print dp

getting parse error on input `='

Why is that so?

Upvotes: 1

Views: 222

Answers (1)

Ganesh Sittampalam
Ganesh Sittampalam

Reputation: 29110

In Haskell source files, top-level definitions like f shouldn't be introduced with a let - just write

f [] = []
f ('\n':',':a) = f ('\n' : a)
f (a:b) = a : f b

Also you need make sure that the left-hand side of each clause in a definition lines up in the same column, as Haskell is indentation-aware. So in this case the f in each clause should be at the very start of each line, as above.

Note that the ghci prompt behaves more like you're inside a do block, and so let is valid, which can be a source of confusion when moving between the two.

Upvotes: 5

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