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From: yogeshwarsing@gmx.com
Newsgroups: comp.lang.ada
Subject: Re: GNAT and Dimension Checking
Date: Sun, 1 Jul 2012 03:44:19 -0700 (PDT)
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Date: 2012-07-01T03:44:19-07:00
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This feature is rather limited though. For example one cannot do conversions. If you have to work with an "irregular" unit, you will have to do the conversion yourself e.g.

with System.Dim.MKS; use System.Dim.Mks;
with System.Dim.Mks_IO; use System.Dim.Mks_IO;
with Text_IO; use Text_IO;

procedure Free_Fall3 is
       subtype Acceleration is Mks_Type
       with Dimension => ("m/s^2", Meter => 1, Second => -2, others => 0);
       G : constant acceleration := 127137.6 * km/(hour ** 2) ;
       T : Time := 10.0/3600.0 * hour;
       Distance : length;

     begin
       Put ("Gravitational constant: ");
       Put (G, Aft => 2, Exp => 0); Put_Line ("");
       Put ("Time: ");
       Put (T, fore => 4, Aft => 4, Exp => 0); Put_Line ("");
       Distance := 0.5 * G * T ** 2;
       Put ("distance travelled in 10 seconds (or 10/3600 hour) of free fall ");
       Put (Distance, fore => 4, Aft => 4, Exp => 0);
       Put_Line ("");
end Free_Fall3; 

You will still get the outputs in the default MKS units. So basically, it is just checking if your dimensions are right.


And I do not think that you are able to deal with record constructs such as

 type Motion_Parameter is
       record
         Radius: Length := 0.0 * m;
         Speed : Velocity := 0.0 * m/s;
         Time_Step    : Time :=  0.0 * s;
         Number_Of_Revolutions : Float := 0.0;
       end record;

since Motion_Parameter will need to have a specific dimension in terms of MKS and having different MKS units in the record structure makes this impossible.

YC