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Formal Modelling in VDM

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stackPP

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Properties Values
Language Version: vdm10
Entry point : n

usestack.vdmpp

class UseStack
instance variables
  stack : Stack := new Stack();
traces
  TracesStack :
    stack.Reset() ;
    let x in set {2,8} in stack.Push(x){1,4};
    (stack.Push(9) | stack.Pop())

end UseStack

stack.vdmpp

class Stack

  instance variables
    stack : seq of int := [];

  operations

    public
    Reset : () ==> ()
    Reset () ==
      stack := [];

    public
    Pop : () ==> int
    Pop() ==
      def res = hd stack in
        (stack := tl stack;
         return res)
    pre stack <> []
    post stack~ = [RESULT]^stack;

    public Push: int ==> ()
    Push(elem) ==
      stack := stack ^[elem];

    public
    Top : () ==> int
    Top() ==
      return (hd stack);

end Stack