passing parameter by reference to a procedure

[adekunleadekoya]

What is wrong with this code ?

/*******************************

set i 30;

proc test {x} {

upvar 1 $x xy;

set x 4;

set xy 2;

return $xy;

}

test $i;

puts $i;

**************************************/

 

[feherke]

Hi

Next time please explain your problem.

set i 30

proc test {x} {

  upvar 1 $x xy

  set  xy 2

}

test i

puts $i

Feherke.

http://rootshell.be/~feherke/

 

[PinkeyNBrain]

To explain the original error, the line of code:
test $i
is parsed as
test 30
because you assigned i a value of 30. Subsequently in your procedure the variable x now has a value of 30. You were doing an upvar against the value 30. You wanted to do an upvar against the value i. Then
upvar 1 $x xy
would parse as
upvar 1 i xy
Which would then cause xy to point to the same thing as i is pointing to. Then, changing xy in the routine will change i globally.