prettyShow.hs

prettyShow :: (Show a, Num a) => SymbolicManip a -> String
prettyShow val = prettyShowPrec 0 val

-- Show a number or symbol as a bare number or serial
prettyShowPrec _ (Number x) = show x
prettyShowPrec _ (Symbol x) = x

prettyShowPrec _ (UnaryArith opstr a) = 
    opstr ++ "(" ++ show a ++ ")"

prettyShowPrec outerPrec (BinaryArith op a b)
        | outerPrec <= innerPrec = pa ++ pop ++ pb
        | otherwise = "(" ++ pa ++ pop ++ pb ++ ")" where 
            pa        = prettyShowPrec innerPrec a
            pb        = prettyShowPrec innerPrec b
            pop       = op2str op
            innerPrec = getPrec op
          

op2str :: Op -> String
op2str Plus = "+"
op2str Minus = "-"
op2str Mul = "*"
op2str Div = "/"
op2str Pow = "**"

getPrec :: Op -> Int
getPrec Plus=5
getPrec Minus=5
getPrec Mul=6
getPrec Div=6
getPrec Pow=7