Hi All, I'm trying to work out how to show the steps in evaluating "How the function is calculated". In other words I want this program to actually print out the steps. For e.g. eval (Multiply(Add(Val 10) (Val 20)) (Val 3) Which is add 10+20 and multiply by 3 = 90 The program then produces( Prints out) something like working: eval (Multiply(Add(Val 10) (Val 20)) (Val 3) working Add(Val10) (Val 20) answer 1 Val 30 answer 2 Val 90 This is what I have so far but it wont even do the calculations. Any help appreciated. data Expression = Val Float | Add Expression Expression | Subtract Expression Expression | Multiply Expression Expression | Divide Expression Expression deriving Show eval :: Expression -> Float eval (Val x) = x eval (Add x y) = eval x + eval y eval (Multiply x y) = eval x * eval y eval (Subtract x y) = eval x - eval y eval (Divide x y) = eval x / eval y John