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with Except;
with Screen_Output;
with Stack;
package body Values.Operations is
----------
-- Read --
----------
function Read (Op : String) return Operation is
begin
if Op = "+" then
return Add;
elsif Op = "-" then
return Sub;
elsif Op = "*" then
return Mul;
elsif Op = "/" then
return Div;
else
raise Except.User_Error;
end if;
end Read;
-------------
-- Process --
-------------
procedure Process (Op : Operation) is
V2 : Value := Stack.Pop;
V1 : Value := Stack.Pop;
Result : Integer;
begin
case Op is
when Add =>
Result := V1.E + V2.E;
when Div =>
Result := V1.E / V2.E;
when Mul =>
Result := V1.E * V2.E;
when Sub =>
Result := V1.E - V2.E;
end case;
-- Create an integer Value by setting the field "E" of the record
-- to Result.
Stack.Push (new Value_Info'(E => Result));
exception
-- If we get a Constraint_Error exception, then we had a computation
-- overflow or a divide by zero.
when Constraint_Error =>
Screen_Output.Error_Msg ("Operation error. Values popped.");
end Process;
end Values.Operations;
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