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Practical Programming in Tcl & Tk, Third Edition
By Brent B. Welch

Table of Contents
Part I.  Tcl Basics

Chapter 8. Tcl Arrays

This chapter describes Tcl arrays, which provide a flexible mechanism to build many other data structures in Tcl. Tcl command described is: array.

An array is a Tcl variable with a string-valued index. You can think of the index as a key, and the array as a collection of related data items identified by different keys. The index, or key, can be any string value. Internally, an array is implemented with a hash table, so the cost of accessing each array element is about the same. Before Tcl 8.0, arrays had a performance advantage over lists that took time to access proportional to the size of the list.

The flexibility of arrays makes them an important tool for the Tcl programmer. A common use of arrays is to manage a collection of variables, much as you use a C struct or Pascal record. This chapter shows how to create several simple data structures using Tcl arrays.

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