[Haskell-beginners] sqrt root issues

30 Jun 2010

      Hi all,

I'm having a real hard time wrapping my head around a problem;

Here is a basic, no frills, function.
prime divisor divided
    | divided == 1 = True
    | divisor== divided= True
    | mod divided divisor== 0 = False
    | otherwise = next_prime
    where next_prime = prime (divisor + 2) divided

and the calling function:
is_prime input = prime 3 input

I'm trying to get the square root of input as an Integer.

In GHCI:
:t (toInteger $ round $ sqrt 25)
(toInteger $ round $ sqrt 25) :: Integer

but if I change is_prime input = prime 3 (toInteger $ round $ sqrt input)

I get this error:
problem3.hs:19:33:
     No instance for (RealFrac Integer)
       arising from a use of `round' at problem3.hs:19:33-37
     Possible fix: add an instance declaration for (RealFrac Integer)
     In the first argument of `($)', namely `round'
     In the second argument of `($)', namely `round $ sqrt input'
     In the expression: toInteger $ round $ sqrt input

problem3.hs:19:41:
     No instance for (Floating Integer)
       arising from a use of `sqrt' at problem3.hs:19:41-50
     Possible fix: add an instance declaration for (Floating Integer)
     In the second argument of `($)', namely `sqrt input'
     In the second argument of `($)', namely `round $ sqrt input'
     In the expression: toInteger $ round $ sqrt input
Failed, modules loaded: none.

Can someone please help me out and tell me what I'm missing?

Thanks in advance,

Bryce

[Haskell-beginners] sqrt root issues

Bryce Verdier