set /a x=1,y=2,z=x + y

#2
Looks like yet another silly CMD extension. Why not just write

V:\> set /a x=1 & set /a y=2 & set /a z=x + y

One little interesting thing I noticed. With Vince's requested syntax,
CMD only displays the 3, while with mine (which also works for both TCC
and CMD), it displays 123 for CMD, and 1 / 2 / 3 (with the slashes to
indicate line breaks). Slightly different output. OK, so my request
isn't 100% compatible between TCC and CMD either. Well, at least it
works!

________________________________

From: vefatica [mailto:]
Sent: Thursday, June 05, 2008 9:57 AM
To: Mickey Ferguson
Subject: [Support-t-139] set /a x=1,y=2,z=x + y

Is there any chance that you'd include this capability of CMD?

v:\> set /a x=1,y=2,z=x + y
3
v:\> echo %x% %y% %z%
1 2 3
--
- Vince
 
#3
On Thu, 05 Jun 2008 12:35:58 -0500, you wrote:


>Looks like yet another silly CMD extension. Why not just write
>
>V:\> set /a x=1 & set /a y=2 & set /a z=x + y
Silly?

set /a x=1,y=2,z=x + y

is a lot easier to write and, I'd bet, a lot faster to execute.
--
- Vince
 
#4
I highly doubt it makes any execution time difference. With a .bat file
you have to load each line separately (interpreted), so you can run into
performance issues when they are on separate lines. But we've got the
'&' now, with everything all on one line, so that's not an issue. In
today's world of extremely fast processors, I can't see how it could
make much of a difference, unless you're talking about many millions of
executions, and even then, only a little bit. I might be wrong about my
assessment, but I would be very surprised if I was.

And besides, if you really have a process that is so extensive, is the
command processor a good choice for language? Performance should almost
never be a priority consideration for batch processing, as long as the
difference is not significant.

________________________________

From: vefatica [mailto:]
Sent: Thursday, June 05, 2008 10:43 AM
To: Mickey Ferguson
Subject: RE: [Support-t-139] set /a x=1,y=2,z=x + y

On Thu, 05 Jun 2008 12:35:58 -0500, you wrote:


Quote:

>Looks like yet another silly CMD extension. Why not just write
>
>V:\> set /a x=1 & set /a y=2 & set /a z=x + y
Silly?

set /a x=1,y=2,z=x + y

is a lot easier to write and, I'd bet, a lot faster to execute.
--
- Vince
 
#5
On Thu, 05 Jun 2008 13:13:57 -0500, you wrote:


>I highly doubt it makes any execution time difference. With a .bat file
>you have to load each line separately (interpreted), so you can run into
>performance issues when they are on separate lines. But we've got the
>'&' now, with everything all on one line, so that's not an issue.
But three commands have to be parsed instead of one.

Anyway, according to the help, "SET /A is included for compatibility with
CMD.EXE".
--
- Vince
 
#7
On Thu, 05 Jun 2008 15:36:38 -0500, you wrote:


>> Is there any chance that you'd include this capability of CMD?
>>
>> v:\> set /a x=1,y=2,z=x + y

>Why? (Unless you're trying to obfuscate your code, I don't see any
>reason for it.)
It's perfectly clear to me. It's easier to write than the alternative and I'd
bet it is (or could be) faster. Those are the reasons I ask for it. I don't
care a whit about CMD compatibility (but it's occasionally a good lever).
--
- Vince
 

rconn

Administrator
Staff member
May 14, 2008
10,506
94
#8
vefatica wrote:


> Quote:
> >> Is there any chance that you'd include this capability of CMD?
> >>
> >> v:\> set /a x=1,y=2,z=x + y
>
> Quote:
> >Why? (Unless you're trying to obfuscate your code, I don't see any
> >reason for it.)
>
> It's perfectly clear to me. It's easier to write than the alternative
> and I'd
> bet it is (or could be) faster. Those are the reasons I ask for it.
It won't be any faster, and it certainly won't be any easier to read.

This is undocumented behavior for CMD -- have you seen anybody using
this in CMD code?

It also would break existing code, as it means you would not be able to
use thousands separators in your argument -- for example, try this in in
TCC and CMD:

set /a x=123,456

For some of our non-US users, replace "would not be able to use
thousands separators" with "would not be able to use decimal separators".

All in all, I think it's poorly-thought-out syntax (assuming it's a CMD
feature, and not a bug!), and I don't intend to change TCC.

Rex Conn
JP Software
 
#9
>> >> Is there any chance that you'd include this capability of CMD?
>> >> v:\> set /a x=1,y=2,z=x + y

> This is undocumented behavior for CMD -- have you seen anybody using
> this in CMD code?
First, I am not arguing for a change, nor even its frequency of usage,
just quibbling about the "undocumented" bit. From CMD, I typed HELP
SET and in the order of precedence, it shows "," as "expression
separator" which I interpret as documenting the behavior.

I saw several things in CMD's SET help that I'd never seen before.

--
2008 Fridays: 4/4, 6/6, 8/8, 10/10, 12/12 and 5/9, 9/5, 7/11, 11/7.
Next year they're Saturday.
Measure wealth by the things you have for which you would not take money.
 
#11
On Thu, 05 Jun 2008 16:49:42 -0500, you wrote:


>It won't be any faster, and it certainly won't be any easier to read.
Here's a simple-minded version called SETA (even works).

INT WINAPI SETA ( WCHAR * psz )
{
WCHAR *p = wcstok(psz, L","), szCmd[8192];
while ( p )
{
Sprintf(szCmd, L"/A %s", p);
Set_Cmd(szCmd);
p = wcstok(NULL, L",");
}
return 0;
}

It seems to be about 20-25% faster. See the test below.

v:\> type seta.btm
echo Using SET /A:
timer /q
do i=1 to 10000
set /a x=1 & set /a y=2 & set /a z=x + y
enddo
timer
echo Using SET /A on separate lines
timer /q
do i=1 to 10000
set /a x=1
set /a y=2
set /a z=x + y
enddo
timer
echo Using SETA:
timer /q
do i=1 to 10000
seta x=1, y=2, z=x + y
enddo
timer

v:\> seta.btm
Using SET /A:
Timer 1 off: 20:21:42 Elapsed: 0:00:04.27
Using SET /A on separate lines
Timer 1 off: 20:21:46 Elapsed: 0:00:04.57
Using SETA:
Timer 1 off: 20:21:50 Elapsed: 0:00:03.39

--
- Vince