Re: Cannot use NULL as identifier?

["Marin David Condic" <marin.condic.auntie.spam@pacemicro.com>]

Null is a reserved word in Ada - used as a null statement and as a value for
access types, etc. You can't use it as an identifier.

What you probably want is ASCII.Nul - notice only one 'l'.

Also, unless you are interfacing to some C/C++ routines, you do not need to
terminate strings with Nul. You are much better off using the attributes
'First, 'Last, 'Range, etc. along with the string handling routines you'll
find in Ada.Strings, Ada.Strings.Fixed, Ada.Strings.Bounded,
Ada.Strings.Unbounded. (My personal favorite is to use Ada.Strings.Unbounded
for just about everything. It will have some speed/space penalties over
fixed strings, but you'd really have to have an intense application to start
noticing the difference.)

BTW, you probably don't want to use the package ASCII since it is falling
out of vogue and may eventually go away. More appropriately, you should use
Ada.Characters.Latin_1 which also contains a constant called "Nul".

If you have not done so already, you will want to get hold of an Ada95
Reference Manual (plenty of electronic sources). To really get all the
benefits of Ada, you'll want to look over all the appendices and at least be
cognizant of the language defined packages and what they contain. That way,
when you need a resource (like character constants, math routines, string
manipulation, etc.) you'll at least have a vague memory of what is available
and know where to look for more help. I repeatedly find myself in there
digging up routines to leverage someone else's work! :-)

MDC
--
Marin David Condic
Senior Software Engineer
Pace Micro Technology Americas    www.pacemicro.com
Enabling the digital revolution
e-Mail:    marin.condic@pacemicro.com
Web:      http://www.mcondic.com/


"McDoobie" <someone@nospam.net> wrote in message
news:Ad6R6.1259$DG1.337725@news1.rdc1.mi.home.com...
> I've written a small program that parses the contents of different
> directories and searches for duplicate files.
>
> I have an assignment that reads
>
> FilePath : constant string := "tesfile.xxx" & ASCII.NULL;
>
> Now, the GNAT compiler on Linux gives me the error
> "reserved word NULL cannot be used as identifier "
>
> Now, I'm using the text_io and gnat.os_lib libraries to compile this, so
> I'm assuming that os_lib makes an allowance for this. However, I could be
> mistaken. I ripped the above code fragement from a website, and the
> website (the Big Book of Linux Ada programming) doesnt appear to  indicate
> that theres a problem with this. (Of course I probably overlooked
> something.)
>
> I'm also searching through "Programming in Ada95"(Barnes) trying to find
> info on this error.
>
> Any tips or pointers would be helpful.
>
> Thanks.
>
> McDoobie
> Chris@dont.spam.me