CODEWITHSUNDEEP
haskell
Ohad
Ohad

Reputation: 1631

Haskell - parse error on input

I have just started using Haskell interpreter.

Can anyone tell me what's wrong with this code:(for Fibonacci) 

fib :: Int -> Int
fib n
|n==0 =0
|n==1 =1
|n>1  =fib(n-2) + fib(n-1)

I am getting this error message:

 fib.hs:3:1: parse error on input `|'
 [1 of 1] Compiling Main             ( fib.hs, interpreted )
 Failed, modules loaded: none.

Upvotes: 0

Views: 459

Answers (2)

chi
chi

Reputation: 116139

You have to indent the next lines at least one space, e.g.:

fib :: Int -> Int
fib n
 |n==0 =0
 |n==1 =1
 |n>1  =fib(n-2) + fib(n-1)

Upvotes: 1

Ørjan Johansen
Ørjan Johansen

Reputation: 18189

Haskell is indentation sensitive. In particular the |'s need to be indented further than the function name:

fib :: Int -> Int
fib n
  |n==0 =0
  |n==1 =1
  |n>1  =fib(n-2) + fib(n-1)

Also, it is more idiomatic to use pattern matching for comparing with a constant:

fib :: Int -> Int
fib 0 =0
fib 1 =1
fib n
  |n>1  =fib(n-2) + fib(n-1)

Upvotes: 4

Related Questions