Re: New_Page

Re: New_Page

[Georg Bauhaus]

On Wed, 2006-11-01 at 13:39 +0200, Tapio Marjomäki wrote:
> Hi,
>  
> could somebody tell why the procedure below does not run as expected?

>  
> with Ada.Text_IO; use Ada.Text_IO;
> -- with Ada.Characters.Latin_1; use Ada.Characters.Latin_1;
> procedure Page is

$ ./page |cat -v
 0
New page
^LNew page
^LNew page
^L

I believe the ^L is called a format effector, to be interpreted
by the printer or terminal.

-- Georg 

Re: New_Page

[Jeffrey R. Carter]

Tapio Marjom�ki wrote:
>  
> could somebody tell why the procedure below does not run as expected?

Probably because you have unreasonable expectations. Since we don't know 
what your expectations are, we can't be more specific. It would also 
help if we knew what compiler you were using.

New_Page typically puts one or more control characters ("format 
effectors") into the specified file (with no explicit file, this is 
Current_Output; if not explicitly set, Current_Output is 
Standard_Output). What those characters are is up to the compiler 
writer. What those characters do when sent to various output devices is 
up to the creators of those output devices.

It is likely that the new-page character(s) output by your compiler are 
those that cause a new page on some device other than a Windows console, 
and are not those needed by a Windows console.

In short, New_Page is device-specific, should probably not have been 
included in Text_IO, and should be avoided in portable SW.

-- 
Jeff Carter
"My mind is a raging torrent, flooded with rivulets of
thought, cascading into a waterfall of creative alternatives."
Blazing Saddles
89

Re: New_Page

[Robert A Duff]

"Jeffrey R. Carter" <spam.not.jrcarter@acm.not.spam.org> writes:

> In short, New_Page is device-specific, should probably not have been
> included in Text_IO, and should be avoided in portable SW.

New_Line isn't exactly portable, either.  ;-)

- Bob

Re: New_Page

[Jeffrey R. Carter]

Robert A Duff wrote:
> 
> New_Line isn't exactly portable, either.  ;-)

What it outputs isn't always portable to other platforms, that's for 
sure. On the intended platform, though, it usually works OK.

-- 
Jeff Carter
"My mind is a raging torrent, flooded with rivulets of
thought, cascading into a waterfall of creative alternatives."
Blazing Saddles
89

Re: New_Page

[Tapio Marjom�ki]

... so we can say that New_Page doesn't work on MS XP console application on 
GNAT Ada compiler?

"Jeffrey R. Carter" <spam.not.jrcarter@acm.not.spam.org> wrote in message 
news:dwc2h.1047017$084.491837@attbi_s22...
> Robert A Duff wrote:
>>
>> New_Line isn't exactly portable, either.  ;-)
>
> What it outputs isn't always portable to other platforms, that's for sure. 
> On the intended platform, though, it usually works OK.
>
> -- 
> Jeff Carter
> "My mind is a raging torrent, flooded with rivulets of
> thought, cascading into a waterfall of creative alternatives."
> Blazing Saddles
> 89 

Re: New_Page

[Pascal Obry]

Tapio Marjom�ki a �crit :
> .... so we can say that New_Page doesn't work on MS XP console application on 
> GNAT Ada compiler?

No, we can say that the Windows console does not handle a new page code
(FF - ASCII#12).

Pascal.

-- 

--|------------------------------------------------------
--| Pascal Obry                           Team-Ada Member
--| 45, rue Gabriel Peri - 78114 Magny Les Hameaux FRANCE
--|------------------------------------------------------
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Re: New_Page

[Keith Thompson]

Robert A Duff <bobduff@shell01.TheWorld.com> writes:
> "Jeffrey R. Carter" <spam.not.jrcarter@acm.not.spam.org> writes:
>
>> In short, New_Page is device-specific, should probably not have been
>> included in Text_IO, and should be avoided in portable SW.
>
> New_Line isn't exactly portable, either.  ;-)

New_Line produces an end-of-line marker.  The way this is represented
varies from one system to another, but this is a *very* well-known
issue, and translating from one format to another is extremely common.

New_Page produces an end-of-page marker.  Most systems don't even have
such a thing.

I agree that all the page-oriented stuff should have been left out of
the language.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
San Diego Supercomputer Center             <*>  <http://users.sdsc.edu/~kst>
We must do something.  This is something.  Therefore, we must do this.

Re: New_Page

[Robert A Duff]

Keith Thompson <kst-u@mib.org> writes:

> Robert A Duff <bobduff@shell01.TheWorld.com> writes:
>> "Jeffrey R. Carter" <spam.not.jrcarter@acm.not.spam.org> writes:
>>
>>> In short, New_Page is device-specific, should probably not have been
>>> included in Text_IO, and should be avoided in portable SW.
>>
>> New_Line isn't exactly portable, either.  ;-)
>
> New_Line produces an end-of-line marker.  The way this is represented
> varies from one system to another, but this is a *very* well-known
> issue, and translating from one format to another is extremely common.

Indeed.  It's sad, but true.

> New_Page produces an end-of-page marker.  Most systems don't even have
> such a thing.

Well, control-L is pretty widely recognized as a form-feed, at least on
hardware where that makes sense.

> I agree that all the page-oriented stuff should have been left out of
> the language.

Not sure whom you're agreeing with, but I agree with that, too.

I think Text_IO is badly designed, for many reasons, including this
one.

- Bob

> We must do something.  This is something.  Therefore, we must do this.

;-)