with Ada.Text_IO; use Ada.Text_IO;

procedure Typing is
  -- Notes:
  -- Every "built-in" type in Ada is defined with facilities generally available
  -- to the user.

  ------------------------------------------------------------------------------
  -- Ranged integers.
  ------------------------------------------------------------------------------
  type My_Int is range -1 .. 20;

  function Overflow (X : My_Int) return My_Int is
  begin
    return X + 1;
  end Overflow;

  procedure Test_My_Int is
    -- N overflows.
    --N : My_Int := Overflow (My_Int'Last);

    -- C is equal to (12 + 15) / 2 = 13.
    -- The reason C does not overflow is that type-level overflows are performed
    -- at specific boundaries for efficiency reasons, in this case when the
    -- result of the computation is assigned to the variable C. The value 13 is
    -- within the range of My_Int, so we do not get an overflow exception in this
    -- case.
    A : My_Int := 12;
    B : My_Int := 15;
    C : My_Int := (A + B) / 2;
  begin
    for I in My_int loop
      Put_Line (My_Int'Image (I));
    end loop;

    --Put_Line ("My_Int N = " & My_Int'Image (N));
    Put_Line ("My_Int C = " & My_Int'Image (C));
  end Test_My_Int;

  ------------------------------------------------------------------------------
  -- Unsigned integers / modular types.
  ------------------------------------------------------------------------------
  type Mod_Int is mod 5;

  procedure Test_Mod_Int is
    A : Mod_Int := 2;
    B : Mod_Int := 4;
    C : Mod_Int := A + B; -- C = 1. No overflow, implicit mod operation.
  begin
    Put_Line ("Mod_Int C = " & Mod_Int'Image (C));
  end Test_Mod_Int;

  ------------------------------------------------------------------------------
  -- Enumerations.
  ------------------------------------------------------------------------------
  type Days is (Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday);

  procedure Test_Days is
  begin
    for D in Days loop
      Put (Days'Image (D));
      case D is
        when Monday .. Friday => Put_Line (" -> weekday");
        when Saturday .. Sunday => Put_Line (" -> weekend");
      end case;
    end loop;
  end Test_Days;

  ------------------------------------------------------------------------------
  -- Floats with ranges.
  ------------------------------------------------------------------------------
  type T_Norm is new Float range -1.0 .. +1.0;

  procedure Test_T_Norm is
    A : T_Norm := 0.5;
  begin
    Put_Line ("A = " & T_Norm'Image (A));
  end Test_T_Norm;

  ------------------------------------------------------------------------------
  -- Casting.
  ------------------------------------------------------------------------------
  type Meters is new Float;
  type Miles is new Float;

  procedure Test_Units is
    Dist_Imperial : Miles;
    Dist_Metric : constant Meters := 100.0;
  begin
    Dist_Imperial := Miles (Dist_Metric) / 1609.0;
    Put_Line (Meters'Image (Dist_Metric) & " meters is " & Miles'Image (Dist_Imperial) & " miles");
  end Test_Units;

  ------------------------------------------------------------------------------
  -- Derived types.
  --
  -- Derived types introduce a new type and usually constrain the parent type.
  ------------------------------------------------------------------------------
  type SSN is new Integer range 0 .. 999_99_9999;

  procedure Test_SSN is
    X : SSN := 111_22_3333;
  begin
    Put_Line("SSN X = " & SSN'Image (X));
  end Test_SSN;

  ------------------------------------------------------------------------------
  -- Subtypes types.
  --
  -- Subtypes express constraints without introducing a new type.
  -- Constraints are enforced at runtime.
  ------------------------------------------------------------------------------
  subtype Weekend_Days is Days range Saturday .. Sunday;

  procedure Test_Subtypes is
    A : Weekend_Days := Saturday;
    B : Days := A; -- OK.
  begin
    Put_Line ("Day B is " & Days'Image (B));
    --A := Monday; -- Runtime exception.
  end Test_Subtypes;

begin
  Test_My_Int;
  Test_Mod_Int;
  Test_Days;
  Test_T_Norm;
  Test_Units;
  Test_SSN;
  Test_Subtypes;
end Typing;