Procedures example 3: adding two numbers

----------------------------------------------------------------
-- program to read in and add two integers.
-- This is an example to illustrate procedures with parameters.
-- X. Yao, 18/05/97
----------------------------------------------------------------

with text_io; use text_io;

procedure add_two_numbers is

  package int_io is new text_io.integer_io(integer); use int_io;

  first_num,			-- first integer from the user
  second_num,			-- second integer from the user
  sum:		integer;	-- result of addition of the above two

  procedure get_an_int (number: out integer) is
    -- This procedure reads in an integer from the keyboard
  begin -- get_an_int
    put ("Please enter an integer: ");
    get (number); skip_line;
    new_line;
  end get_an_int;

  procedure add_nums (num1, 			-- first integer to be added
		      num2: in integer; 	-- second integer to be added
		      total: out integer	-- result of addition
		      ) is
    -- This procedure add two integers
  begin 
    total := num1 + num2;
  end add_nums;

  procedure show_answer (number: in integer	-- integer to be displayed
			) is
    -- display an integer on the screen
  begin 
    new_line;
    put ("The total is ");
    put (number, width=>1);
    put (".");
    new_line(2);
  end show_answer;

begin -- add_two_numbers

  get_an_int (first_num);
  get_an_int (second_num);
  add_nums (first_num, second_num, sum);
  show_answer (sum);

end add_two_numbers;