hashmap - Duplicate keys in tcl associative array

Question

I am using associative array/hash map to store some data. I want to keep duplicate entries that have same key but different values. Currently, the previous key is being overwritten by the last instance.

key: LVL values: vdd,vddr

key: LVL values: vddi,vdd

Answer 1

Multimaps are, in general, implemented as ordinary maps to lists of items. (There's a few other ways, algorithmically, but they're rare in practice except in a few degenerate cases.) In Tcl, you do this by appending to the list in the element on creation and using nested loops on read out:

# With arrays
foreach {key item} $thingsToPutIn {
    lappend map($key) $item
}

foreach {key items} [array get map] {
    foreach item $items {
        puts "$key => $item"
    }
}

# With dictionaries
foreach {key item} $thingsToPutIn {
    dict lappend map $key $item
}

dict for {key items} $map {
    foreach item $items {
        puts "$key => $item"
    }
}