[Haskell-beginners] Puzzling type error

[Logesh Pillay]

I've written the following implementation of the algorithm in this 
article http://www.afjarvis.staff.shef.ac.uk/maths/jarvisspec02.pdf

sqRoot n scale = sqRoot' (5*n) 5
  where
  sqRoot' a b
    | floor (logBase 10 b) >= scale = div b 10
    | a >= b                        = sqRoot' (a-b) (b+10)
    | otherwise                     = sqRoot' (a*100) ((100 * (div b 
10)) + (mod b 10))

Since this involves whole numbers only, I was surprised by the following 
run-time error.

*Main> sqRoot 2 5

<interactive>:1:0:
    Ambiguous type variable `t' in the constraints:
      `RealFrac t' arising from a use of `sqRoot' at <interactive>:1:0-9
      `Floating t' arising from a use of `sqRoot' at <interactive>:1:0-9
      `Integral t' arising from a use of `sqRoot' at <interactive>:1:0-9
    Probable fix: add a type signature that fixes these type variable(s)

What am I missing?

Logesh Pillay