Why C dont allow the name of a variable start with a digit?

[Jason20005]

Dear all,

Why C and some of other languages dont allow the name of a variable
start with a digit?

[Richard Heathfield]

Chris McDonald said:

<snip>

>
The question was actually about *starting* with a digit,
which doesn't necessarily imply consisting *only* of digits.

Yes, I know, but I figured (correctly, as it turns out) that using an
all-digit example would bring the point home to the OP very quickly.

But what about: long int 42L = 6;

0X0 also springs to mind.

Forgive me - this is supposed to be a non-commercial channel.

0x20.

There - that's better.

--
Richard Heathfield <http://www.cpax.org.uk>
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999

[Bartc]

"Jason20005" <ja********@gmail.comwrote in message
news:79**********************************@h1g2000p rh.googlegroups.com...

Dear all,

Why C and some of other languages dont allow the name of a variable
start with a digit?

It's been explained there could be ambiguity between integer constants and
variables.

It might have been feasible where there was no ambiguity (so 0XABC must be a
constant, but 0XABG must an identifier), but it's unsatisfactory. Some other
way of distinguishing constants and identifiers would be needed, and this
would offset some advantage of starting with a digit.

More useful (to me anyway) would have been the ability to use $ in an
identifier (available on some Cs but not standard). Then it could have been
used in place of _, which is difficult to see and can be confused with __
and ___.

--
Bart

[Martin]

On Fri, 11 Apr 2008 10:23:05 +0100, Bartc <[e-mail]:

More useful (to me anyway) would have been the ability to use $ in an
identifier

Indeed. VAX/VMS's DCL allowed dollar-signs, e.g. F$SEVERITY.

--
Martin

[Mark McIntyre]

Martin wrote:

On Fri, 11 Apr 2008 10:23:05 +0100, Bartc <[e-mail]:

>More useful (to me anyway) would have been the ability to use $ in an
identifier

Indeed. VAX/VMS's DCL allowed dollar-signs, e.g. F$SEVERITY.

Still does allow it. So does VaxC if I recall correctly.

--
Mark McIntyre

CLC FAQ <http://c-faq.com/>
CLC readme: <http://www.ungerhu.com/jxh/clc.welcome.txt>

[Chad]

On Apr 12, 3:01*pm, Mark McIntyre <[e-mail]:

Martin wrote:

On Fri, 11 Apr 2008 10:23:05 +0100, Bartc <[e-mail]:

More useful (to me anyway) would have been the ability to use $ in an
identifier

Indeed. VAX/VMS's DCL allowed dollar-signs, e.g. F$SEVERITY.

Still does allow it. So does VaxC if I recall correctly.

--

I thought VMS was the actual operating system and that the VAX was the
corresponding hardware. I vaguely remember one of the labs at HP
having FreeBSD running on a VAX.

[Keith Thompson]

Mark McIntyre <ma**********@spamcop.netwrites:

Martin wrote:

>On Fri, 11 Apr 2008 10:23:05 +0100, Bartc <[e-mail]:

>>More useful (to me anyway) would have been the ability to use $ in an
identifier

Indeed. VAX/VMS's DCL allowed dollar-signs, e.g. F$SEVERITY.

Still does allow it. So does VaxC if I recall correctly.

Last time I used it, yes.

Whether DCL allows dollar signs isn't particularly relevant; that's
the command language, equivalent to a shell on Unix-like systems. But
the VMS (now OpenVMS) dialect(s) of C does allow dollar signs in
identifiers, used mostly for calling native system routines that have
dollar signs in their names. gcc also supports this extension.

(The two major C compilers for VAX/VMS are VAXC and DECC; the latter
is also supported on Alpha/VMS.)

Of course this is non-standard.

--
Keith Thompson (The_Other_Keith) <ks***@mib.org>
Nokia
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"