China DOS Union

@echo off
set a=one
set b=two
echo/Before call :swap a b
call :Swap a b
echo/After call 1 :swap a b
call :Swap b a
echo/After call 2 :swap b a
pause
goto :EOF

:Swap
call set a=%%%1%%
call set b=%%%2%%
set "%1=%b%" & set "%2=%a%" & goto :EOF

----------------------------------------------------------------------
Displayed result:
Before call :swap a b
After call 1 :swap a b
After call 2 :swap b a

I really can't figure it out, please explain..

When it gets to echo/After call 2 :swap b a
call set a=%%%1%%
call set b=%%%2%%
because %1=b, %2=a
that is,
set a=!b!
set b=!a!
so as far as the values are concerned, !a!=!b!=one

[ Last edited by Hanyeguxing on 2010-4-12 at 14:04 ]

Your reply again, thanks first of all!!

Oh, so that's how it is!!

I was treating the variables brought in by CALL as values and doing call set on them, no wonder two disappeared... uh