How do I create and iterate through a hash of hashes in TCL?

Question

How do I create and iterate through a hash of hashes in TCL?

If I have data like:

foo = {
    a => {
        aa => { aa1 aa2 aa3 }
        ab => { ab1 ab2 ab3 }
        ac => { ac1 ac2 ac3 }
    }
    b => {
        ba => { ba1 ba2 ba3 }
        bb => { bb1 bb2 bb3 }
        bc => { bc1 bc2 bc3 }
    }
    c => {
        ca => { ca1 ca2 ca3 }
        cb => { cb1 cb2 cb3 }
        cc => { cc1 cc2 cc3 }
    }
}

How do I create such a hash by inserting one leaf-node data item at a time. Something like:

lappend foo(a)(ab) "ab1"

Then how do I iterate over all data elements? like:

foreach key in foo {
    foreach sub_key in foo($key) {
        foreach elem in foo($key)($sub_key) {
            puts "foo\($key\)\($sub_key\) is $elem"
        }
    }
}

Edit : Unfortunately, I do not have access to the newer 'dict' construct.

Answer 1

If you're not using Tcl 8.5, then you can use arrays. Note that arrays are one-dimensional, but the key is an arbitrary string that can be used to fake multi-dimensionality:

array set foo {}
foreach first {a b c} {
    foreach second {a b c} {
        foreach third {1 2 3} {
            lappend foo($first,$first$second) "$first$second$third"
        }
    }
}
parray data

and output it -- note: array keys, unlike dictionary keys, are unordered:

foreach key [array names foo] {
    foreach elem $foo($key) {
        puts "$key\t$elem"
    }
}

If you are given the keys (example 'b' and 'bc') you can get the value thusly:

set key1 b
set key2 bc
foreach elem $foo($key1,$key2) {puts $elem}