Newbie Visibility Problem TEXT_IO.INTEGER_IO

Newbie Visibility Problem TEXT_IO.INTEGER_IO

[bm34mailing<<SPAM-SUCKS>>]

Hi All:

I am very new to Ada and am having a visibility problem that I am not 
sure how to get around. I am trying to build the "MostUltimateAnswer" 
sample application from the LAW web site (Section 1.2.12).

http://www.scism.sbu.ac.uk/law/Section1/chap2/s1c2p12.html

I have ensured that I copied the source code verbatim (less the line 
numbers) and get the following errors:

D:\Projects\Personal\ada>gnatmake -f -u MostUltimateAnswer.adb
gcc -c mostultimateanswer.adb
mostultimateanswer.adb:15:25: "Text_Io" is not visible
mostultimateanswer.adb:15:25: non-visible declaration at a-textio.ads:51
mostultimateanswer.adb:16:08: "Intio" is undefined
mostultimateanswer.adb:47:04: invalid parameter list in call (use -gnatf 
for det
ails)
mostultimateanswer.adb:58:04: invalid parameter list in call (use -gnatf 
for det
ails)
gnatmake: "mostultimateanswer.adb" compilation error

Can someone give me a hint as to the problem? I am using GNAT 3.15p and 
am thinking that I am missing a library or some settings need to be 
changed. At the beginning of the program, I do have the lines:

with Ada.Text_IO;
use Ada.Text_Io;

so I believe Text_io should be visible.

However, the tutorial or any reference I can find make no mention of 
having to change settings.

I have successfully built "UltimateAnswer" as shown in 1.2.1 with no 
problems.

http://www.scism.sbu.ac.uk/law/Section1/chap2/s1c2p1.html

Thanks,

Bill

Re: Newbie Visibility Problem TEXT_IO.INTEGER_IO

[Simon Wright]

"bm34mailing<<SPAM-SUCKS>>" <"bm34mailing<<SPAM-SUCKS>>"@yahoo.ca> writes:

> with Ada.Text_IO;
> use Ada.Text_Io;
> 
> so I believe Text_io should be visible.

Well, no, that use makes the contents of text_io visible, not the
thing itself.

You could try just "use Ada;" or the following .. (I haven't tried it,
too much grief retyping :-)

0007 with ADA.TEXT_IO; 
0008 use  ADA.TEXT_IO;                     <<<<<<<<< remove this line
0009  
0010 procedure MostUltimateAnswer is 
0011 
        package Text_IO renames Ada.Text_IO;

0012    package IntIo is new TEXT_IO.INTEGER_IO( INTEGER ); 
0013    use IntIO; 


-- 
Simon Wright                               100% Ada, no bugs.

Re: Newbie Visibility Problem TEXT_IO.INTEGER_IO

[bm34mailing<<SPAM-SUCKS>>]

Hi Simon:

Thanks for the response. I tried to use your suggestion, but I still 
could not build the app. However, I considered your thought on visibility:

<snip>

 > Well, no, that use makes the contents of text_io visible, not the
 > thing itself.

<snip>

I added the lines:

with Ada;
use Ada;

to make the contents of Ada (i.e Text_IO) visible. This works as I 
expected. This does not seem like the best way to resolve the problem, 
but I am less than two days into learning about Ada, so I will reserve 
final judgment until my understanding of the syntax improves.

Thanks again for the help Simon. I appreciate the quick response.

Bill

"
Simon Wright wrote:
> "bm34mailing<<SPAM-SUCKS>>" <"bm34mailing<<SPAM-SUCKS>>"@yahoo.ca> writes:
> 
> 
>>with Ada.Text_IO;
>>use Ada.Text_Io;
>>
>>so I believe Text_io should be visible.
> 
> 
> Well, no, that use makes the contents of text_io visible, not the
> thing itself.
> 
> You could try just "use Ada;" or the following .. (I haven't tried it,
> too much grief retyping :-)
> 
> 0007 with ADA.TEXT_IO; 
> 0008 use  ADA.TEXT_IO;                     <<<<<<<<< remove this line
> 0009  
> 0010 procedure MostUltimateAnswer is 
> 0011 
>         package Text_IO renames Ada.Text_IO;
> 
> 0012    package IntIo is new TEXT_IO.INTEGER_IO( INTEGER ); 
> 0013    use IntIO; 
> 
> 

Re: Newbie Visibility Problem TEXT_IO.INTEGER_IO

[Martin Krischik]

bm34mailing wrote:

> with Ada;
> use Ada;
> 
> to make the contents of Ada (i.e Text_IO) visible. This works as I
> expected. This does not seem like the best way to resolve the problem,
> but I am less than two days into learning about Ada, so I will reserve
> final judgment until my understanding of the syntax improves.

For a beginner the best option is not to use "use" at all. OK, you have to
type a lot more but understanding will be better.

Later, when you have the understanding use "use" selective. "with" need to
be placed before package - "use" does not:

with Ada.Text_IO;

package ...

  procedure ...
  is
     use Ada.Text_IO;
  begin
  end ...;

end ...;

is just as vaild. And the reason why there are two of them.

With Regards

Martin
-- 
mailto://krischik@users.sourceforge.net
http://www.ada.krischik.com

Re: Newbie Visibility Problem TEXT_IO.INTEGER_IO

[bm34mailing<<SPAM-SUCKS>>]

Thanks to all for the help with this problem. Martin, Dimtry and Dennis 
all made good points that I will remember going forward.

Thanks again to Simon for the original answer.

Bill

Martin Krischik wrote:

> bm34mailing wrote:
> 
> 
>>with Ada;
>>use Ada;
>>
>>to make the contents of Ada (i.e Text_IO) visible. This works as I
>>expected. This does not seem like the best way to resolve the problem,
>>but I am less than two days into learning about Ada, so I will reserve
>>final judgment until my understanding of the syntax improves.
> 
> 
> For a beginner the best option is not to use "use" at all. OK, you have to
> type a lot more but understanding will be better.
> 
> Later, when you have the understanding use "use" selective. "with" need to
> be placed before package - "use" does not:
> 
> with Ada.Text_IO;
> 
> package ...
> 
>   procedure ...
>   is
>      use Ada.Text_IO;
>   begin
>   end ...;
> 
> end ...;
> 
> is just as vaild. And the reason why there are two of them.
> 
> With Regards
> 
> Martin

Re: Newbie Visibility Problem TEXT_IO.INTEGER_IO

[Dmitry A. Kazakov]

bm34mailing wrote:

> I am very new to Ada and am having a visibility problem that I am not
> sure how to get around. I am trying to build the "MostUltimateAnswer"
> sample application from the LAW web site (Section 1.2.12).
> 
> http://www.scism.sbu.ac.uk/law/Section1/chap2/s1c2p12.html
>
> Can someone give me a hint as to the problem? I am using GNAT 3.15p and
> am thinking that I am missing a library or some settings need to be
> changed. At the beginning of the program, I do have the lines:
> 
> with Ada.Text_IO;
> use Ada.Text_Io;
> 
> so I believe Text_io should be visible.

It isn't.

I will try to explain it. In the program you have:

   package IntIo is new TEXT_IO.INTEGER_IO( INTEGER );

Here Text_IO is not visible, because it is declared in the package Ada. Thus
the variant

(A)

with Ada.Text_IO;
use Ada.Text_IO;

use Ada; -- This makes Text_IO visible!
...
   package IntIo is new TEXT_IO.INTEGER_IO( INTEGER );

You can also use the full name of Integer_IO, the following variant:

(B)

with Ada.Text_IO;
...
   package IntIo is new ADA.TEXT_IO.INTEGER_IO( INTEGER );
                     -- The fully qualified name

Though Integer_IO is already visible as other posters noted, so the variant:

(C)

with Ada.Text_IO;
use Ada.Text_IO;
...
   package IntIo is new INTEGER_IO( INTEGER );
                     -- Ada.Text_IO.Integer_IO is visible

And finally, for backward compatibility with Ada 83, there is the package
Text_IO (renamed Ada.Text_IO). Probably that misled the code author, who
mixed both old and new nomenclature. So to complete the picture, in Ada 83
style:

(D)

with Text_IO;
...
   package IntIo is new TEXT_IO.INTEGER_IO( INTEGER );

-- 
Regards,
Dmitry A. Kazakov
www.dmitry-kazakov.de