ghci

<interactive>:72:1:
    No instance for (RealFrac a0) arising from a use of `split'
    The type variable `a0' is ambiguous
    Possible fix: add a type signature that fixes these type variable(s)
    Note: there are several potential instances:
      instance RealFrac Double -- Defined in `GHC.Float'
      instance RealFrac Float -- Defined in `GHC.Float'
      instance Integral a => RealFrac (GHC.Real.Ratio a)
        -- Defined in `GHC.Real'
    In the expression: split 10 10
    In an equation for `it': it = split 10 10

<interactive>:72:7:
    No instance for (Num a0) arising from the literal `10'
    The type variable `a0' is ambiguous
    Possible fix: add a type signature that fixes these type variable(s)
    Note: there are several potential instances:
      instance Num Double -- Defined in `GHC.Float'
      instance Num Float -- Defined in `GHC.Float'
      instance Integral a => Num (GHC.Real.Ratio a)
        -- Defined in `GHC.Real'
      ...plus three others
    In the first argument of `split', namely `10'
    In the expression: split 10 10
    In an equation for `it': it = split 10 10

hoge.hs

split x n = val : [other]                                                             
  where d = floor $ logBase n x 
        digit = n ^ d 
        val = floor $ x / digit
        other = x - val * digit