-- Inputs 2 numbers in range 0 .. 999 and prints whether they are reverse of each other

-- Demonstrates declaring and calling a procedure
-- A procedure is equivalent to a method with a void return type (eg void println() )
-- Procedures are used as statements!

pragma Ada_2012;  -- Make sure 2012 compiler is used
with ada.text_io; use ada.text_io; 
with ada.integer_text_io; use ada.integer_text_io; 
procedure proc1  is 
    subtype Digit is Natural range 0 .. 9;
    subtype Small_Nat is Natural range 0 .. 999;

    function ones_dig(n: Small_Nat) return Digit is (n mod 10);
    function tens_dig(n: Small_Nat) return Digit is ((n / 10) mod 10);
    function hundreds_dig(n: Small_Nat) return Digit is (n / 100);

    function eq_rev(n1, n2: Small_Nat) return Boolean is
        eq1, eq10, eq100: Boolean;
    begin
        eq1 := ones_dig(n1) = hundreds_dig(n2);
        eq10 := tens_dig(n1) = tens_dig(n2);
        eq100 := hundreds_dig(n1) = ones_dig(n2);
        return eq1 and eq10 and eq100;
    end eq_rev;

    procedure check_nums(sm1, sm2: Small_Nat) is
    begin
        put(sm1'img & " and " & sm2'img & " are");
        if eq_rev(sm1, sm2) then       -- Function returns a value
            put(" THE SAME");
        else
            put(" are DIFFERENT");
        end if;
        put_line(" in reverse");
    end check_nums;

    s1, s2: Small_Nat;
begin
    get(s1);
    get(s2);

    check_nums(s1, s2);    -- Call procedure as a statement

exception
    when constraint_error => put_line("Value out of range");
    when others => put_line("Error occurred");
end proc1;

-- Input: 123 321
-- Output: 123 and  321 are THE SAME in reverse
  
-- Input: 123 123
-- Output: 123 and  123 are DIFFERENT in reverse