Is this explanation correct?

Is this explanation correct?

[chris.danx]

Hi,

The ps-programming@tutoraid.org mailing list seems a little dead at the minute
and it seems like the Ada folk are busy (I am no expert and don't want to
perpetuate misinformation).


A newbie posted asking

"There is something I don't understand about
end_of_file stuff. When I key in my data on the file in the floppy drive, if
I leave and save a space after the end data, I will get an End_Error . but
when I open the file back, and get rid of that space and save, and run the
program it works fine. can you tell me why?"


I want to check this before I relay it to the mailing list.


The program uses Ada.Integer_text_io which ignores spaces, so when the program
get's to the space it thinks there's an integer after it and it doesn't find
one, so it generates the end_error (exception) to let us know.


Is this correct?

Cheers,
Chris

Re: Is this explanation correct?

[Jeffrey Carter]

"chris.danx" wrote:
> 
> A newbie posted asking
> 
> "There is something I don't understand about
> end_of_file stuff. When I key in my data on the file in the floppy drive, if
> I leave and save a space after the end data, I will get an End_Error . but
> when I open the file back, and get rid of that space and save, and run the
> program it works fine. can you tell me why?"
> 
> I want to check this before I relay it to the mailing list.
> 
> The program uses Ada.Integer_text_io which ignores spaces, so when the program
> get's to the space it thinks there's an integer after it and it doesn't find
> one, so it generates the end_error (exception) to let us know.
> 
> Is this correct?

It might be better to say that, with the space at the end of the file,
Ada.Integer_Text_IO.Get will stop before the space, so End_Of_File will
return False. Then the next call to Ada.Integer_Text_IO.Get will read
past the end of file looking for an Integer, causing End_Error to be
raised. With the space removed, Ada.Integer_Text_IO.Get will stop before
the line/page/file terminator, so End_Of_File will return True, and the
program will terminate normally.

-- 
Jeff Carter
"I wave my private parts at your aunties."
Monty Python & the Holy Grail