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    Types: TextFile
    Names: »V«

└─⟦a7d1ea751⟧ Bits:30000550 8mm tape, Rational 1000, !users!projects 94_04_11
    └─ ⟦129cab021⟧ »DATA« 
        └─⟦this⟧ 
└─⟦a7d1ea751⟧ Bits:30000550 8mm tape, Rational 1000, !users!projects 94_04_11
    └─ ⟦129cab021⟧ »DATA« 
        └─⟦e24fb53b7⟧ 
            └─⟦this⟧ 

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with Alias;
with Output_Stream;  
with Slot;
generic  
    type User_Defined_Operators is (<>);

    with function User_Defined_Unary_Evaluate
                     (Using_Operator : User_Defined_Operators;
                      Right          : Slot.Object) return Slot.Object is <>;
    with function User_Defined_Binary_Evaluate
                     (Using_Operator : User_Defined_Operators;
                      Left, Right    : Slot.Object) return Slot.Object is <>;

    with function User_Defined_Image
                     (Op : User_Defined_Operators) return String is
       User_Defined_Operators'Image;

package Generic_Expression is

    type Object is private;
    Null_Expression : constant Object;

    -- primary expression constructors

    function Value (For_Object : Slot.Object) return Object;

    function Value (For_Integer : Integer)     return Object;
    function Value (For_Boolean : Boolean)     return Object;
    function Value (For_Float : Float)         return Object;
    function Value (For_Character : Character) return Object;
    function Value (For_Duration : Duration)   return Object;
    function Value (For_String : String)       return Object;

    function Value (For_Alias : Alias.Name) return Object;

    -- user defined expression constructors

    generic
        Operator : User_Defined_Operators;
    function Unary_User_Expression (Right : Object) return Object;

    generic
        Operator : User_Defined_Operators;
    function Binary_User_Expression (Left, Right : Object) return Object;

    -- general operations

    function  Evaluate (The_Expression : Object) return Slot.Object;
    procedure Put      (The_Object : Object; Where : Output_Stream.Object);

    package System_Defined_Expression is

        function "+" (Left, Right : Object) return Object;
        function "-" (Left, Right : Object) return Object;
        function "*" (Left, Right : Object) return Object;
        function "/" (Left, Right : Object) return Object;
        function "&" (Left, Right : Object) return Object;

        function "-"   (Right : Object) return Object;
        function "abs" (Right : Object) return Object;

    end System_Defined_Expression;

    Illegal_Operation : exception;  
private

    type Sub_Classes is (Primary, Unary, Binary, Undefined);
    type Object_Structure (Sub_Class : Sub_Classes);
    type Object      is access Object_Structure;
    Null_Expression : constant Object := null;

end Generic_Expression;