(* Formalinterpeter: I have Unäry Predikates for example:  "a", "b", "c". I have a Formal Postfixform with Operators NOT, AND and OR. For example: "a AND b OR NOT c" (Infix) gives: "a b AND c NOT OR" (Postfix).
 I should write a function interpret(formula, dect) that returns a unary predicte that evaluates the formal *)

I have tried something like this :-/


    let pred =
        [ "a", true;
          "b", true;
          "c", false; ]
       // |> Map.ofList;; (* Convert list to Map *)

    let pred = [("a", true); ("b", true); ("c", false)]

    let formelinterprter (??? ) =
    match x with
    | :? AND -> //delete x y then append "x and y"
    | :? OR ->  // delete x y then append "x or y"
    | :? NOT -> // delete x then append "x not"
    | _ -> printfn "The input is something else"



I found a solution in Python:


# 11. interpret
lang = {'a': True,
        'b': True,
        'c': False
       }
def interpret(formula, d):
    stack = []
    for w in formula.split():
        if w == 'AND':
            x,y = (stack.pop(), stack.pop())
            stack.append(x and y)
        elif w == 'OR':
            x,y = (stack.pop(), stack.pop())
            stack.append(x or y)
        elif w == 'NOT':
            x = stack.pop()
            stack.append(not x)
        else:
            stack.append(d[w])
        print w, stack
    return stack[0]

print interpret('a b AND c NOT AND', lang)