Modular Types

Modular Types

Modular Types

• Example modular type: minutes.adb (prettified)


• Values of type minuteType range from 0 to 59 and they wrap
• Arithmetic for type minuteType wraps

with Ada.Text_IO;
procedure minutes is

    type MinuteType is mod 60;

	package Minute_IO is new Ada.Text_IO.Modular_IO (Num => MinuteType);
	use Minute_IO;

    m: MinuteType;

 begin
    m := 50;
    m := m + 20;
    put(m);    -- Outputs 10
    

Input and Output

• Type MinuteType is not predefined - how to we do I/O with it?


• Must instantiate the package Ada.Text_IO.Modular_IO

      with Ada.Text_IO;
      procedure minutes is

         type MinuteType is mod 60;

         package Minute_IO is new Ada.Text_IO.Modular_IO (Num => MinuteType);
         use Minute_IO;

         m: MinuteType;

      begin
         m := 50;
         put(m);
    

Bitwise Operations

• Modular types allow some bitwise operations such as and, or, not, xor:

    type Unsigned_Byte is mod 256;
    u: Unsigned_Byte := 2#0011_0101#
    v: Unsigned_Byte := 2#1111_0000#

    w: Unsigned_Byte := u and v;
    y: Unsigned_Byte := u or v;
    z: Unsigned_Byte := u xor v;
    

• We must create a new package for IO, since MinuteType is newly defined

Type Checking

• Types with different names can not be mixed
• Except for subtypes

Type Conversion

• Types with different names can not be mixed

      with Ada.Text_IO;
      with Ada.Integer_Text_IO; use Ada.Integer_Text_IO;
      procedure minutes is

         type MinuteType is mod 60;

         package Minute_IO is new Ada.Text_IO.Modular_IO (Num => MinuteType);
         use Minute_IO;

         m: MinuteType;
         i, j: Integer;

      begin
         i := m * j;  --  ????
         put(m);
    

• How to convert?
• What does the convert do?