Re: Ada The Best Language?

["Marc A. Criley" <mcqada@earthlink.net>]

Vinzent Hoefler wrote:
> 
> Original Message From taw@users.sourceforge.net
> 
> 
> >- too strong typing
> 
> What? Sorry, but the typing is a great plus. It's true, you have to think a
> little more about it when designing types and sometimes this might be a
> little
> bit annoying ;), but is thinking really that *bad*?
> 
> If nothing helps, there's still the feature of Unchecked Type Conversions.
> At least you were warned then. :)

My nomination for "Best Kept Secret of Ada" is strong typing.  It's
almost always viewed as purely a defensive feature--to help avoid type
mismatches, and so you have to really think through your types, which
can take time, and sometimes be a pain, yadda yadda...

Strong typing lets you _embed_information_ into your program, and then
get it out again via attributes.

Consider this:

   type Altitude is range 0 .. 50_000;
   Above_Ground : Altitude;

The "defensive" interpretation says that you can now be assured an
attempt to assign a negative altitude or go into military airspace will
be immediately caught.

But look at what you get from the "informational" interpretation:
  'First, 'Last, 'Size, 'Range, 'Address, 'Min, 'Max, 'Image, 'Val,
'Pos, 'Value, 'Input, 'Output, 'Read, 'Write, 'Pred, 'Succ, 'Valid,
'Wide_Image, 'Wide_Value, 'Wide_Width, 'Width.

And that's just from a simple little scalar type definition.  Floating
and fixed point types, composite constructs, tasks, and so on, each have
their own specific means of embedding and extracting information.

Ada's strong typing produces "information dense" code.  Simple
declarations, like that of Altitude above, inherently provide
information that would otherwise have to be explicitly maintained or
derived when using other languages.

Marc A. Criley
Senior Staff Engineer
Quadrus Corporation
www.quadruscorp.com