Re: Records that could be arrays

[tmoran@acm.org]

> type Coordinate is
>    record
>       Row    : Local_Float;
>       Column : Local_Float;
>    end record;
  In mathematics, one usually gives a coordinate as (x,y), while in
graphics it's often (vertical, horizontal).  Inadvertently switching
the order can be an annoying bug.  But with
   type Rows is new Local_Float;
   type Cols is new Local_Float;
the compiler's type checking can point out such errors.  In that case,
of course, you have to use a record with
        Row    : Rows;
        Column : Cols;
and cannot use an array.
  If your code might one day have to accomodate 3-D coordinates, then
        for A in Axis loop
          Sum := Sum + V(A)**2;
needs no change, while
        Sum := V.Row**2 + V.Column**2;
will need a makeover, and thus is much less desirable.

  The general point is that sometimes an array fits the problem better
and sometimes a record fits it better.  A rule that says "hey, they're all
Local_Float so it should be an array" is much too limiting.