Introduction

Strings hold textual data from a single character to a large text file. Lists allow us to store groups of strings and lists in an organized manner. But neither offers a simple method for relating data elements to a key value, in the manner of an array or database. If you need to organize multiple items under a single group, nothing beats a dictionary.

Dictionary allows storage of data with a key/value mapping methodology, with each key in the dictionary mapping to a single value. Dictionaries are textual in nature (like how lists are), but allow association between key/value pairs. For example, if I create a dictionary "Fruits" with a key of "Apple" and a value of "17"; I have the beginnings of a simple inventory system. With the addition of nested dictionaries, you can rapidly emulate data storage and retrieval similar to a database application without the overhead of a third-party product.

As with all things in Tcl, we have been provided with a command and a full complement...