ProfitPress Mega CDROM2 …eeware (MSDOS)(1992)(Eng)/ProfitPress-MegaCDROM2.B6I/MAGAZINE/DDJMAG/DDJ8705.ZIP/JONESLST.LST

File List | 1987-04-10 | 8.6 KB | 292 lines

Listing One

--                  DUNITS.ADA
--                  VERSION 1

--                  1 JANUARY 1986
--                  DO-WHILE JONES
--                  324 TRACI LANE
--                  RIDGECREST, CA 93555
--                  [phone]

package DIMENSIONAL_UNITS is

  -- This package provides useful parent types for derived
  -- dimensional units. That is, it makes it possible to
  -- do this:

  --  type Feet is new Integer_Unit;
  --  type Radians is new Float_Unit;

  --  PI           : constant Radians := Type_Convert(3.14159);
  --  TARGET_RANGE : Feet;
  --  ANGLE        : Radians;
  --  REVOLUTIONS  : integer;

  -- These derived data types will inherit all the operations
  -- in the package below. These are all the operations which
  -- make sense for dimensional quantities.

  -- The modulo operation for Float_Units is provided to make
  -- it easy to normalize angular measurements.

  --  ANGLE := ANGLE mod (2.0 * PI);

  -- The division operator for Float_Units which return INTEGERS
  -- truncates toward zero (rather than rounding) to make it consistant
  -- with integer division, and it lets you do this:

  --  REVOLUTIONS := ANGLE / (2.0 * PI);

  type Integer_Unit is private;

  function Type_Convert(X : integer) return Integer_Unit;
    -- Lets you assign values to dimensional objects.
    -- For example,

    -- TARGET_RANGE := Type_Convert(587);

  function "+"(RIGHT : Integer_Unit)
    return Integer_Unit;
  function "-"(RIGHT : Integer_Unit)
    return Integer_Unit;
  function "abs"(RIGHT : Integer_Unit)
    return Integer_Unit;
  function "+"(LEFT, RIGHT : Integer_Unit)
    return Integer_Unit;
  function "-"(LEFT, RIGHT : Integer_Unit)
    return Integer_Unit;
  function "*"(LEFT : integer; RIGHT : Integer_Unit)
    return Integer_Unit;
  function "*"(LEFT : Integer_Unit; RIGHT : integer)
    return Integer_Unit;
  function "/"(LEFT : Integer_Unit; RIGHT : integer)
    return Integer_Unit;
  function "/"(LEFT, RIGHT : Integer_Unit)
    return integer;
  function "/"(LEFT, RIGHT : Integer_Unit)
    return float;
  function "rem"(LEFT, RIGHT : Integer_Unit)
    return Integer_Unit;
  function "mod"(LEFT, RIGHT : Integer_Unit)
    return Integer_Unit;
  function Dimensionless(LEFT : Integer_Unit)
    return integer;
  function Dimensionless(LEFT : Integer_Unit)
    return float;

  -- "=" and "/=" are already defined for private types
  function "<"(LEFT, RIGHT : Integer_Unit)
    return boolean;
  function "<="(LEFT, RIGHT : Integer_Unit)
    return boolean;
  function ">"(LEFT, RIGHT : Integer_Unit)
    return boolean;
  function ">="(LEFT, RIGHT : Integer_Unit)
    return boolean;

  type Float_Unit is private;

  function Type_Convert(X : float) return Float_Unit;
    -- Lets you assign values to dimensional objects.
    -- For example,

    -- ANGLE := Type_Convert(3.14159);

  function "+"(RIGHT : Float_Unit)
    return Float_Unit;
  function "-"(RIGHT : Float_Unit)
    return Float_Unit;
  function "abs"(RIGHT : Float_Unit)
    return Float_Unit;
  function "+"(LEFT, RIGHT : Float_Unit)
    return Float_Unit;
  function "-"(LEFT, RIGHT : Float_Unit)
    return Float_Unit;
  function "*"(LEFT : integer; RIGHT : Float_Unit)
    return Float_Unit;
  function "*"(LEFT : Float_Unit; RIGHT : integer)
    return Float_Unit;
  function "*"(LEFT : float; RIGHT : Float_Unit)
    return Float_Unit;
  function "*"(LEFT : Float_Unit; RIGHT : float)
    return Float_Unit;
  function "/"(LEFT : Float_Unit; RIGHT : integer)
    return Float_Unit;
  function "/"(LEFT : Float_Unit; RIGHT : float)
    return Float_Unit;
  function "/"(LEFT, RIGHT : Float_Unit)
    return integer; -- trucates toward zero
  function "/"(LEFT, RIGHT : Float_Unit)
    return float;
  function "rem"(LEFT, RIGHT : Float_Unit)
    return Float_Unit;
  function "mod"(LEFT, RIGHT : Float_Unit)
    return Float_Unit;
  function Dimensionless(LEFT : Float_Unit)
    return integer;
  function Dimensionless(LEFT : Float_Unit)
    return float;

  -- "=" and "/=" are already defined for private types
  function "<"(LEFT, RIGHT : Float_Unit)
    return boolean;
  function "<="(LEFT, RIGHT : Float_Unit)
    return boolean;
  function ">"(LEFT, RIGHT : Float_Unit)
    return boolean;
  function ">="(LEFT, RIGHT : Float_Unit)
    return boolean;

-- The following don't have any application to dimensional
-- problems. I almost hid them in the package body, but I
-- thought that since I needed them to derive some of the
-- Float_Unit operations someone else might need them, too.

  function "/"(LEFT, RIGHT : float) return integer;
    -- divide and truncate toward zero

  function "rem"(LEFT, RIGHT : float) return float;

  function "mod"(LEFT, RIGHT : float) return float;

private

  type Integer_Unit is new integer;
  type Float_Unit is new float;

end DIMENSIONAL_UNITS;





Listing Two

--                    DUEX.ADA
-- This is an example of how the use of dimensional units as data
-- types improves program clarity.

------------------------- Compilation Unit 1 --------------------------

with DIMENSIONAL_UNITS; use DIMENSIONAL_UNITS;
package SPEED_GUN_UNITS is

  type Miles_per_hour is new Integer_Unit;
  type Hertz is new Float_Unit;
  type Miles_per_second is new Float_Unit;

  function Type_Convert(X : Miles_per_second)
   return Miles_per_hour;

  function "*"(LEFT : Miles_per_second; RIGHT : float)
   return Miles_per_hour;

end SPEED_GUN_UNITS;

------------------------- Compilation Unit 2 --------------------------

with SPEED_GUN_UNITS; use SPEED_GUN_UNITS;
package HARDWARE_CIRCUITS is
  function Xmit_Frequency_Measurement return Hertz;
  function Doppler_Frequency_Measurement return Hertz;
  procedure put(X : Miles_per_hour);
end HARDWARE_CIRCUITS;

------------------------- Compilation Unit 3 --------------------------

with HARDWARE_CIRCUITS; use HARDWARE_CIRCUITS;
with SPEED_GUN_UNITS; use SPEED_GUN_UNITS;
procedure Speed_Gun is
  TRANSMIT_FREQUENCY, DOPPLER_FREQUENCY : Hertz;
  SPEED : Miles_per_hour;
  C : constant Miles_per_second
   := Type_Convert(186_280.0); -- speed of light
begin
  TRANSMIT_FREQUENCY := Xmit_Frequency_Measurement;
  DOPPLER_FREQUENCY := Doppler_Frequency_Measurement;
  SPEED := (C / 2.0) * (DOPPLER_FREQUENCY / TRANSMIT_FREQUENCY);
  put(SPEED);
end Speed_Gun;




------------------------- Compilation Unit 4 --------------------------

package body SPEED_GUN_UNITS is

  function Type_Convert(X : Miles_per_second)
   return Miles_per_hour is
    MPH : Miles_per_second;
  begin
    MPH := X * 60 * 60;
    return Type_Convert(Dimensionless(MPH));
  end Type_Convert;

  function "*"(LEFT : Miles_per_second; RIGHT : float)
   return Miles_per_hour is
  begin
    return Type_Convert(LEFT * RIGHT);
  end "*";

end SPEED_GUN_UNITS;

------------------------- Compilation Unit 5 --------------------------

with TEXT_IO; use TEXT_IO;
package body HARDWARE_CIRCUITS is
  -- The statements below are standing in for code which would
  -- read the frequency directly from hardware circuits and
  -- would display speed on an LCD or LED display. Since I'm
  -- using a terminal as a substitute input device I used
  -- TEXT_IO to get and put data.

  package INT_IO is new INTEGER_IO(integer); use INT_IO;
  package F_IO is new FLOAT_IO(float); use F_IO;

  function Xmit_Frequency_Measurement return Hertz is
    F : float;
  begin
    put("What is the Transmit Frequency (in Hertz)? ");
    get(F);
    skip_line; -- TEXT_IO quirk
    return Type_Convert(F);
  end Xmit_Frequency_Measurement;

  function Doppler_Frequency_Measurement return Hertz is
    F : float;
  begin
    put("What is the Doppler Frequency (in Hertz)? ");
    get(F);
    skip_line; -- TEXT_IO quirk
    return Type_Convert(F);
  end Doppler_Frequency_Measurement;

  procedure put(X : Miles_per_hour) is
    I : integer;
  begin
    I := Dimensionless(X);
    put("The speed is "); put(I); put_line(" MPH.");
  end put;

end HARDWARE_CIRCUITS;

------------------------- Test Results --------------------------

$ run speed_gun
What is the Transmit Frequency (in Hertz)? 10.0e9
What is the Doppler Frequency (in Hertz)? 1600.0
The speed is          54 MPH.
$
$ run speed_gun
What is the Transmit Frequency (in Hertz)? 10.0e9
What is the Doppler Frequency (in Hertz)? 1000.0
The speed is          34 MPH.
$
$ run speed_gun
What is the Transmit Frequency (in Hertz)? 10.0e9
What is the Doppler Frequency (in Hertz)? 2000.0
The speed is          67 MPH.
$