Each unique text string or object in a list may be associated with another value. This is done by using the item as an index into the list.
var/params[0]
params["player"] = "James Byond"
params["score"] = 2000
//List now contains ("player","score")
//These are associated with ("James Byond",2000)
usr << "Looping through list items:"
var/p
for(p in params)
usr << "[p] = [params[p]]"
usr << "Looping through array indices:"
var/i
for(i=1,i<=params.len,i++)
p = params[i]
usr << "[p] = [params[p]]"The above example illustrates the typical way in which list associations are managed. Note that an item in the list may be added by assigning its associated value. The example could have started by doing params.Add("player","score"), but that would have been redundant.
Both for loops in the example have the same effect. The first one loops through each item in the list, and displays it along with its associated value. The second loop achieves the same thing by looping through the numerical indices (referred to as array indices as opposed to associative indices).
Since numeric indices are treated differently, accessing the Nth item in the list, you may not assign an associated value to a numeric list item. Associations must have a text string or object reference as the index item. (alist() is an exception to this, and can use numeric associations. See **BROKEN LINK: /list/alist** for more information.)
Associated values default to null if none is assigned. This is also the value returned when the supplied index item does not exist in the list. The list defined above, for example, would return null for params["time"].
The list() or alist() instructions may also be used to create associative lists.
var/list/lst = list("player" = "James Byond", "score" = 2000)When the index values happen to be text strings that satisfy all the requirements for variable names, this may also be written in a convenient short-hand:
var/list/lst = list(player = "James Byond", score = 2000)In other words, this is exactly the same syntax as for named arguments.
The alist proc creates lists that are strictly associative. This means that list items are treated as “keys” in key,value pairs. Unlike a regular list, each “key” is unique.