[newbie] Need som feedback on code snip

[newbie] Need som feedback on code snip

[Preben Randhol]

I wondered if somebody could take a peep at the code snip below and
comment on it. It works, but is is the Right Way to do it or is there
a smarter way. I'm learning Ada95 on my own and could need some feedback
from somebody experienced with Ada.



-- Just a small test to see how I can change the content of a string
-- variable when I do not know the length of the new or old text.

with Text_IO; use Text_IO;
with Ada.Strings.Unbounded; use Ada.Strings.Unbounded;

procedure myTest is
   Orig_Text : aliased Unbounded_String := To_Unbounded_String("Hello world!");
   type String_ptr is access all Unbounded_String;
   Text_pointer : String_ptr;

begin
   Put_Line(To_String(Orig_Text));
   Text_Pointer := Orig_Text'Access;
   Text_Pointer.all := To_Unbounded_String("Hello yourself!");
   Put_Line(To_String(Orig_Text));
end myTest;

Thanks in advance...

-- 
Preben Randhol                 Affliction is enamoured of thy parts, 
[randhol@pvv.org]              And thou art wedded to calamity. 
[http://www.pvv.org/~randhol/]                    -- W. Shakespeare 

Re: [newbie] Need som feedback on code snip

[Ted Dennison]

In article <m31zan4l1n.fsf@kiuk0156.chembio.ntnu.no>,
  Preben Randhol <randhol@pvv.org> wrote:
>
> comment on it. It works, but is is the Right Way to do it or is there
> a smarter way. I'm learning Ada95 on my own and could need some
> feedback from somebody experienced with Ada.
>
> with Text_IO; use Text_IO;
> with Ada.Strings.Unbounded; use Ada.Strings.Unbounded;
>

If it were me, I'd get rid of the "aliased", String_Ptr, and
Text_Pointer (and the silly hungarian routine name). All you really need
is:

 procedure My_Test is
    Text : Unbounded_String := To_Unbounded_String("Hello world!");
 begin
    Put_Line(To_String(Text));
    Text := To_Unbounded_String("Hello yourself!");
    Put_Line(To_String(Text));
 end My_Test;

There's no point in aliasing things when you don't have to, and it can
cause serious maintanence headaches in larger programs.

--
T.E.D.


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Re: [newbie] Need som feedback on code snip

[Ted Dennison]

In article <7uqilp$g1p$1@nnrp1.deja.com>,
  Ted Dennison <dennison@telepath.com> wrote:
> In article <m31zan4l1n.fsf@kiuk0156.chembio.ntnu.no>,
>   Preben Randhol <randhol@pvv.org> wrote:
> >
> > comment on it. It works, but is is the Right Way to do it or is

>  procedure My_Test is

Btw: if my formatting looks wierd, *don't* emulate it. Deja-news likes
to mundge whitespace in postings. (sigh).

--
T.E.D.


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Before you buy.

Re: [newbie] Need some feedback on code snip

[Matthew Heaney]

In article <m31zan4l1n.fsf@kiuk0156.chembio.ntnu.no> , Preben Randhol 
<randhol@pvv.org>  wrote:

> -- Just a small test to see how I can change the content of a string
> -- variable when I do not know the length of the new or old text.
>
> with Text_IO; use Text_IO;
> with Ada.Strings.Unbounded; use Ada.Strings.Unbounded;
>
> procedure myTest is
>    Orig_Text : aliased Unbounded_String := To_Unbounded_String("Hello
world!");
>    type String_ptr is access all Unbounded_String;
>    Text_pointer : String_ptr;
>
> begin
>    Put_Line(To_String(Orig_Text));
>    Text_Pointer := Orig_Text'Access;
>    Text_Pointer.all := To_Unbounded_String("Hello yourself!");
>    Put_Line(To_String(Orig_Text));
> end myTest;

Don't use heap or pointers.  All of that is hidden behind
Unbounded_String.

  procedure MyTest is
    Text : Unbounded_String := To_Unbounded_String ("hello world");
  begin
    Put_Line (To_String (Text));
    Text := To_Unbounded_String ("Hello yourself");
    Put_Line (To_String (Text));
  end;

Re: [newbie] Need som feedback on code snip

[Robert I. Eachus]

  Can I take this one?  Can I?  Can I please... ;-)

Preben Randhol wrote:
  
> I wondered if somebody could take a peep at the code snip below and
> comment on it.

  It works way too hard to do something which is very simple...

> It works, but is is the Right Way to do it or is there
> a smarter way.

-- Just a small test to see how I can change the content of a string
-- variable when I do not know the length of the new or old text.

with Text_IO; use Text_IO;
with Ada.Strings.Unbounded; use Ada.Strings.Unbounded;
 
procedure My_Test is
   Text :  Unbounded_String := To_Unbounded_String("Hello world!");
begin
   Put_Line(To_String(Text));
   Text := To_Unbounded_String("Hello yourself!");
   Put_Line(To_String(Text));
end My_Test;

   Unbounded strings do for you all that ugly pointer and memory
allocation and reclamation stuff that you have to worry about in C. 
And,
if you are using GNAT, there is a package Ada.Strings.Unbounded.Text_IO,
that makes it still easier:

with Ada.Strings.Unbounded; use Ada.Strings.Unbounded;
with Ada.Strings.Unbounded.Text_IO; use Ada.Strings.Unbounded.Text_IO;
procedure Test2 is
   Text: Unbounded_String := To_Unbounded_String("Hello world!");
begin
   Put_Line(Text);
   Text := To_Unbounded_String("Hello yourself!");
   Put_Line(Text);
end Test2;
 
-- 

                                        Robert I. Eachus

with Standard_Disclaimer;
use  Standard_Disclaimer;
function Message (Text: in Clever_Ideas) return Better_Ideas is...

Re: [newbie] Need som feedback on code snip

[Preben Randhol]

"Robert I. Eachus" <eachus@mitre.org> writes:

|   Can I take this one?  Can I?  Can I please... ;-)

Take what? Sorry I don't understand.
 
|    Unbounded strings do for you all that ugly pointer and memory
| allocation and reclamation stuff that you have to worry about in C. 
| And,
| if you are using GNAT, there is a package Ada.Strings.Unbounded.Text_IO,
| that makes it still easier:

Ah thanks.

Thanks to everybody for replying!

The reason that I used aliased was that I wanted to see how it
worked. I agree that one should not use it for this simple example
though. Sorry for not commenting it.
-- 
Preben Randhol                 Affliction is enamoured of thy parts, 
[randhol@pvv.org]              And thou art wedded to calamity. 
[http://www.pvv.org/~randhol/]                    -- W. Shakespeare