Chained Dictionary Assignment

In this and the follow up Sorted Dictionary studio, you will build three implementations of a dictionary. Each will be a persistent, mutable data structure, so you can expect to use the ref feature of SML, either directly or via the mutable Array structure.

signature DICTIONARY = sig
    type (''k,'v) dictionary
    val get : ((''k,'v) dictionary *''k) -> 'v option
    val put : ((''k,'v) dictionary *''k *'v) -> 'v option
    val remove : ((''k,'v) dictionary *''k) -> 'v option
    val entries : (''k,'v) dictionary -> (''k*'v) list
    val keys : (''k,'v) dictionary -> ''k list
    val values : (''k,'v) dictionary -> 'v list
end

Background

Refs and Arrays

Spec

get

Behaves much like java.util.Map<K,V>'s get method except instead of returning null or the associated value, it returns an option.

SingleList Implementation

signature SINGLE_LIST_DICTIONARY = sig include DICTIONARY
    val create_simple : unit -> (''k,'v) dictionary
end

Hashtable Implementation

Hash table

SML Array Structure

signature HASHED_DICTIONARY = sig include DICTIONARY
    type ''k hash_function = ''k -> int
    val create_hashed : (int * ''k hash_function) -> (''k,'v) dictionary
end