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Old 01-21-2015, 02:19 AM   #1
Registered: Sep 2005
Posts: 201

Rep: Reputation: 19
tcl procedures and changing variable values inside a procedure

I am trying to avoid use of global variables but I feel like having two left hands with Tcl.

I now tried a simple procedure, hacked it from some examples - it does not work...

proc incr_a_b_upvar { a b c} {
 puts "a = $a"
 puts "b = $b"
 puts "c = $c"
 upvar 1 $a a_sub
 upvar 1 $b b_sub
 set a_sub $a
 set b_sub $b
 puts "a_sub = $a_sub"
 puts "b_sub = $b_sub"
 set a [expr {$a + $c}]
 set b [expr {$b + $c}]
set a 2
set b 3
set c 1
incr_a_b_upvar $a $b $c
puts "a = $a"
puts "b = $b"
puts "c = $c"
In similar examples it should actually work without those
two set commands inside the procedure
 set a_sub $a
 set b_sub $b
but without them I get:
a = 2
b = 3
c = 1
can't read "a_sub": no such variable
while executing
"puts "a_sub = $a_sub""
(procedure "incr_a_b_upvar" line 10)
invoked from within
"incr_a_b_upvar $a $b $c"
(file "incr_a_b.tcl" line 30)
So what gives?


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