Duplicate Key in Associative List (Alist)

Description

A duplicate key entry -- if the alist is designed properly -- could be used as a constant time replace function. However, duplicate key entries could be inserted by mistake. Because of this ambiguity, duplicate key entries in an association list are not recommended and should not be allowed.

Demonstrations

The following examples help to illustrate the nature of this weakness and describe methods or techniques which can be used to mitigate the risk.

Note that the examples here are by no means exhaustive and any given weakness may have many subtle varieties, each of which may require different detection methods or runtime controls.

Example One

The following code adds data to a list and then attempts to sort the data.

alist = []
while (foo()): #now assume there is a string data with a key basename
  queue.append(basename,data)
  queue.sort()

Since basename is not necessarily unique, this may not sort how one would like it to be.

See Also