# Unloading an array of inputs as local variables in a proc

# FIRST Solution - read only

# Problem: We have a whole series of values in our main program which
# we wish to access in a proc, but we don't want to have them
# all declared as global.

# Solution: Define all the values in an array, and then call a proc
# inside each proc in which they're needed to copy them into separate
# variables.

# Note: With this solution, the variables are in effect READ ONLY in
# the procs in which they are unpacked - you'll see in my example how
# I have incremented one of the unpacked variables, but this has NOT
# altered the array.

# proc describe is the proc in which the variables are needed
# proc loadshares is the unloader proc, whic works via uplevel to set
# variables with "describe" and any other procs it's called in
# the array share in the top (global) scope is the array of values to
# be made available in the proc describe

proc loadshares {} {
        global share
        foreach key [array names share] {
                uplevel set $key $share($key)
        }
}

proc describe {} {

        loadshares

        incr delegates

        set response "I'm in $town "
        append response "teaching $subject "
        append response "in $month "
        append response "to $delegates people."

        return $response
        }

set share(town) Dublin
set share(subject) Tcl
set share(month) February
set share(delegates) 18

set text [describe]

puts $text
parray share

exit

--------------------------------------------------------------

Sample Output

munchkin:ftcl grahamellis$ tclsh knots
I'm in Dublin teaching Tcl in February to 19 people.
share(delegates) = 18
share(month) = February
share(subject) = Tcl
share(town) = Dublin
munchkin:ftcl grahamellis$