Passing a dictionary value to and fro in TCL

I am trying to write a script which uses a dictionary value to store some data. I am then using the same dictionary value to a procedure for further processing. It looks something like this :

proc testProc {a} {
   some statements ...
   dict incr a key2 1
}

set dummy [dict create]
dict incr dummy key1 1
testProc $dummy 

puts "[dict get $dummy]"

I expected to get output as :

key1 1 key2 1

Instead I got :

key1 1

If I want my output first one , then how should i do it.

Thanks

Solution 1:

testProc updates a copy of the dict. You can either return the modified one and save it:

proc testProc {a} {
    # some statements ...
    dict incr a key2 1
    return $a
}

set dummy [dict create]
dict incr dummy key1 1
set dummy [testProc $dummy]
puts [dict get $dummy]

or pass the name of the variable holding the dict and use upvar (Similar to how dict incr etc. works):

proc testProc {aDict} {
    upvar $aDict a
    # some statements ...
    dict incr a key2 1
}

set dummy [dict create]
dict incr dummy key1 1
testProc dummy
puts [dict get $dummy]