Re: Why is Ada NOT a good choice for a beginner to programming?

[kcline17@hotmail.com (Kevin Cline)]

"Grein, Christoph" <christoph.grein@eurocopter.com> wrote in message news:<mailman.1042181162.27181.comp.lang.ada@ada.eu.org>...
> > > One complaint he had was that it be possible to define a Length
> > > using derived types and still have "*" return values of type Length,
> > > when it should return an area.  He had a point, hadn't he?
> > > OTOH, with only structural equivalence of types, and no way to derive
> > > both an integral length type and an integral area type, that are really
> > > diferent, how can you build areas into your types, such that the compiler
> > > will prevent use of values of the wrong type?
> > > 
> > > In which languages has this been fixed?
> > 
> > This is relatively easy to do in C++.
> > See http://www.fnal.gov/docs/working-groups/fpcltf/html/SIunits-summary.html
> 
> This is also easy in Ada.
> 
> For a collection of methods how to deal with dimensions in Ada, see
> <http://home.T-Online.de/home/Christ-Usch.Grein/Ada/Dimension.html>

Christopher,

I apologize for not noticing that you were referring to your own paper.
But in the paper you mention numerous shortcomings
of the implementation:

  "Ada is not suited to handling physical dimensions!"

and

  ...we can include semantic information within variable declarations...

  g: Meter_Per_Second_2 := 9.81;
  t: Second             := 10.0;
  s: Meter              := 0.5 * g * t**2;
  
  It is the programmer's own responsibility that this formula is physically 
  correct, no type checking is done! 

  ...There is one service restriction: 
    Checks in assignments concerning physical dimensions are not performed. 

The C++ solution affords full compile-time checking of assignments,
and will not allow a quantity of one dimensionality to be assigned
to a variable of another dimensionality except by resorting to
a reinterpret-cast.