Re: ADA Popularity Discussion Request

[Georg Bauhaus <sb463ba@l1-hrz.uni-duisburg.de>]

Kevin Cline <kevin.cline@gmail.com> wrote:

:>    generic
:>       type FPT is digits <>;
:>    package Computations is ...
: 
: Yes, you could have, if you had thought of it before your team wrote
: 100,000 lines of code.

OK, if the code has not used proper types right from the start
and there will be no corrections, there is little you can do but write
adequate code.

: But we're not omniprescient.

Sure. This is why things can be described in fairly abstract
terms. This does *not* mean chosing a concrete type for their
representation. If I know "we will be computing with floating point
values", I won't blindly chose one concrete predefined
floating point type unless there is good reason to do so.
In particular when it costs next to nothing to provide for
possible changes in the type by making the corresponding module a
parameterized module.

:   This
: flexibility also comes with a cost -- it makes the code harder to
: read.  Everyone knows what digits<> means, but the first time we see
: FPT we'll have to go look it up.

As a Client, you won't have to use the name "FPT", see below.

:  Should we also create a type for
: discrete inventory quantity, or just use integer?  Well, it's possible
: that we could need to go to 64 bits, but right now we don't have
: enough memory to expand them all to 64 bits, so better create a IQTY
: type.  And so it goes... soon you have dozens or hundreds of data
: types, and no one knows what they all mean, and the code is obscured
: by type conversions.

So that's it :-) You want the illusion of knowing the type. :-)
And to look at the details by trial and error testing?
Given the information present in digits<>, conceptually, and leaving it at
that, of course will give you lots of opportunities for additional testing
:-) :-)

FPT is of course a name chosen for the sake of this example, not to
be used in real programs to denote a particulat floating point type.
The name does _not_ appear outside the floating point module.

In

  package ... is new  Stone_Carving_Drawings (Float_Type => ...);

it is pretty clear what Float_Type => ... stands for, isn't it?


-- Georg