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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada,comp.lang.c++
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Subject: Re: Teaching new tricks to an old dog (C++ -->Ada)
Date: Thu, 10 Mar 2005 17:25:24 -0600
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Xref: g2news1.google.com comp.lang.ada:9074 comp.lang.c++:45021
Date: 2005-03-10T17:25:24-06:00
List-Id: <comp.lang.ada>

"Jim Rogers" <jimmaureenrogers@att.net> wrote in message
news:4%PXd.358789$w62.304065@bgtnsc05-news.ops.worldnet.att.net...
Jim Rogers wrote:

I would have done this program somewhat differently.

> with Ada.Text_Io;
> with Ada.Numerics.Discrete_Random;
>
> procedure Random_Fill is
>    type Rand_Values is range 0..10_000;
>    package My_Rand is new Ada.Numerics.Discrete_Random(Rand_Values);
>
>    Seed : My_Rand.Generator;
>    subtype Index_Type is Natural range 1..1000;
>    Vec : array(Index_Type) of Rand_Values;
>    Found : Natural := 0;
> begin
>    My_Rand.Reset(Seed); -- seeds the random number generator
>
>    -- fill the array with random values in the range of 0
>    -- through 10,000
>    for I in Vec'range loop
>       Vec(I) := My_Rand.Random(Seed);
>    end loop;

Much better to use an aggregate here:

     Vec := (others => My_Rand.Random(Seed));

The random function will get called once for each component. Let the
compiler write the loop; it can't do a worse job, and it might actually do
better.

>    -- finds first index where a value is less than 1000
>    for I in Vec'range loop
>       if Vec(I) < 1000 then
>          Found := I;
>          exit;
>       end if;
>    end loop;
>    if Found > 0 then
>       Ada.Text_Io.Put_Line("Number < 1000 found at index" &
>          Natural'Image(Found));
>    else
>       Ada.Text_Io.Put_Line("No number < 1000 was found");
>    end if;

I generally stick a test for 'Last into the loop. But that's more because
I'm lazy.

   -- finds first index where a value is less than 1000
   for I in Vec'range loop
      if Vec(I) < 1000 then
         Ada.Text_Io.Put_Line("Number < 1000 found at index" &
             Natural'Image(I));
             exit;
     elsif I = Vec'Last then
        Ada.Text_Io.Put_Line("No number < 1000 was found");
        exit;
     end if;
   end loop;

But in this case, you really ought to not use a for loop at all:

   declare
      I : Index_Type'Base := Vec'First;
   begin
      while I <= Vec'Last loop
          if Vec(I) < 1000 then
             Ada.Text_Io.Put_Line("Number < 1000 found at index" &
                Natural'Image(I));
             exit;
         end if;
         I := I + 1;
     end loop;
     if I <= Vec'Last then
       Ada.Text_Io.Put_Line("Number < 1000 found at index" &
          Natural'Image(I));
    else
       Ada.Text_Io.Put_Line("No number < 1000 was found");
    end if;
  end;

But of course this is a bit more prone to errors.

The best plan is to use a container function that does the searching, so you
don't have to.

That's probably more on this topic than anyone wanted to know. :-)

> end Random_Fill;

                     Randy Brukardt