TCL access array by reference/name

Question

Let's say I have a regular variable that contains the name of an existing array.

array set myarr {
    key_1 val_2
    key_2 val_2
}

set myvar myarr

I can found nowhere how I can iterate over myarr from myvar!

Just write $myvar where you would otherwise write myarr. Such as in array names $myvar. — Peter Lewerin
– Peter Lewerin, Commented May 22, 2015 at 15:56
Thanks Peter! The following seems to work: foreach {key value} [array get $myvar] { puts "$key => $value" } — Eugeniu Rosca
– Eugeniu Rosca, Commented May 22, 2015 at 16:07

Donal Fellows · Accepted Answer · 2015-05-23 10:56:19Z

2

The variable myvar is a simple variable that is holding the name of another variable. You can use a read from it (with $ or set) anywhere where you'd expect to use the name of the variable:

foreach {key value} [array get $myvar] {
    puts "$key => $value"
}

What you can't do directly is use the name to access the contents of the array. To do that, you'd usually use upvar 0 to map the named thing to something that you can work with more easily:

upvar 0 $myvar v
foreach key [lsort [array names v]] {
    puts "$key => $v($key)"
}

(In this case, and provided you're using Tcl 8.6, you could use the -stride option to lsort to work with array get instead of array names, which would let you avoid making the alias. But that's a different way to achieve the same output really, and only applies if you're doing key-sorted array iteration…)

answered May 23, 2015 at 10:56

Donal Fellows

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