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Newsgroups: comp.lang.ada
Date: Tue, 14 Jan 2020 19:40:50 -0800 (PST)
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Subject: Re: Tally
From: Brad Moore <bmoore.ada@gmail.com>
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Xref: reader01.eternal-september.org comp.lang.ada:57842
Date: 2020-01-14T19:40:50-08:00
List-Id: <comp.lang.ada>

On Tuesday, January 14, 2020 at 2:08:16 PM UTC-7, Jeffrey R. Carter wrote:

> A lot depends on what restraints the problem domain puts on the input val=
ues. If=20
> you can define something like
>=20
> type Input_Number is range 1 .. 10;
>=20
> then you can do something straightforward like
>=20
> type Count_Map is array (Input_Number) of Natural;
>=20
> Count  : Count_Map :=3D (others =3D> 0);
> Number : Input_Number;
> ...
> loop
>     exit when No_More_Numbers;
>=20
>     Number :=3D Next_Number;
>     Count (Number) :=3D Count (Number) + 1;
> end loop;
>=20
> If you can't limit the input numbers to a sufficiently small range that a=
n=20
> object like Count can be declared, then you'll need to use a map, as Hols=
ti=20
> suggested, which is only a little more complicated.
>=20

Just to clarify, I'd say using a Map is more complex (quite a bit actually)=
 in terms of what is happening semantically when the program executes, but =
I think it is worth noting that there is not necessarily much difference in=
 complexity in terms of what the user has to write. As Jeff notes, using a =
map does has the advantage of flexibility, for example in handling sparsely=
 populated data where there is a large range of input values.

e.g.

with Ada.Containers.Ordered_Maps; use Ada;

procedure Main
is
   package Count_Maps is new
     Containers.Ordered_Maps (Key_Type     =3D> Natural,
                              Element_Type =3D> Natural);
  =20
   type Input_Data is array (Natural range <>) of Natural;
  =20
   Input : Input_Data :=3D (2, 3, 8, 2, 2, 2, 7, 2, 3, 4, 8);
  =20
   Counts : Count_Maps.Map;
     =20
begin
   for Number of Input loop
      Counts (Number) :=3D Counts (Number) + 1;
   end loop;
end Main;

Brad