• An array indexed by arbitrary keys, not just consecutive integers.
• Useful when indices are sparse or not known until runtime.
• Index type can be int, string, enum, class, etc.

Declaration & Example

byte assoc[byte];  // Associative array indexed by 'byte'
byte idx = 1;

initial begin
    // Initialize sparse entries (1, 2, 4, 8, ... , 128)
    do begin
        assoc[idx] = idx;
        idx = idx << 1;           // Shift left (multiply by 2)
    end while (idx != 0);

    // Iterate with foreach
    foreach (assoc[i])
        $display("assoc[%h] = %h", i, assoc[i]);

    // Iterate with first/next methods
    if (assoc.first(idx))         // Get first index
        do
            $display("assoc[%h] = %h", idx, assoc[idx]);
        while (assoc.next(idx));  // Get next index until none left

    // Delete specific element
    void'(assoc.first(idx));      // Get first index again
    void'(assoc.delete(idx));     // Delete that index

    // Display number of elements
    $display("The array now has %0d elements", assoc.num());
end

Key Methods: