Re: variable lenght strings

[Martin Krischik <krischik@users.sourceforge.net>]

Jean-Pierre Rosen wrote:

> Randy Brukardt a ï¿œcrit :
> 
>> My opinion is that GNAT is wrong in that case. A.10(7) makes it quite
>> clear that you can't have a file terminator without a line and page
>> terminator in front of it.

> More precisely: a file that doesn't end with a line/page terminator is
> improperly formatted.

There is a world beyond Ada and you might like to read files from there too.

>> I vaguely recall having argued this with Robert Dewar, and I think that
>> they had a different interpretation, based on the idea that a file with a
>> missing CR/LF is incorrect for use with Text_IO. I hope I misremember
>> that, because it is stupid (even if it is logically correct) as it
>> essentially says that you can't read outside generated text files with
>> Text_IO (you can't know whether the file has CR/LFs as required).
>> 
>> But I can understand why they wouldn't want to do this properly, because
>> it is a pain to get right, and it saps the performance of Text_IO (since
>> you have the be prepared to check for implied characters for each one you
>> read).

> No, it's simpler than that.
> 
> In all my programs, I simply never check for End_Of_File, I catch
> End_Error instead. It is simpler in other cases too: if you read
> numbers, and the file is terminated with blank lines, you can get
> End_Error even when End_Of_File is false.

Well you could create a Get_Line with End_Error too. But I like to see where
the "easier" part comes into play:

ￜￜￜpackageￜIOￜￜￜￜￜￜrenamesￜAda.Text_IO;

ￜￜￜfunctionￜGet_Lineￜ(
ￜￜￜￜￜￜFileￜ:ￜinￜIO.File_Type)
ￜￜￜreturn
ￜￜￜￜￜￜString
ￜￜￜis
ￜￜￜￜￜￜBufferￜ:ￜStringￜ(1ￜ..ￜBufferSize);
ￜￜￜￜￜￜLastￜￜￜ:ￜNatural;
ￜￜￜbegin
ￜￜￜￜￜￜIO.Get_Lineￜ(
ￜￜￜￜￜￜￜￜￜFileￜ=>ￜFile,
ￜￜￜￜￜￜￜￜￜItemￜ=>ￜBuffer,
ￜￜￜￜￜￜￜￜￜLastￜ=>ￜLast);

ￜￜￜￜￜￜifￜLastￜ<ￜBuffer'Lastￜthen
ￜￜￜￜￜￜￜￜￜreturnￜBufferￜ(1ￜ..ￜLast);
ￜￜￜￜￜￜelsifￜIO.End_Of_Fileￜ(File)ￜthen
ￜￜￜￜￜￜￜￜￜreturnￜBuffer;
ￜￜￜￜￜￜelse
ￜￜￜￜￜￜￜￜￜreturnￜBufferￜ&ￜGet_Lineￜ(File);
ￜￜￜￜￜￜendￜif;
ￜￜￜendￜGet_Line;

I can see a just as easy - but easier...

With Regards

Martin

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