Book Image

Tcl/Tk 8.5 Programming Cookbook

Book Image

Tcl/Tk 8.5 Programming Cookbook

Overview of this book

With Tcl/Tk, you can create full-featured cross-platform applications in a simple and easy-to-understand way without any expensive development package; the only tools required are a simple text editor and your imagination. This practical cookbook will help you to efficiently interact with editors, debuggers, and shell type interactive programs using Tcl/Tk 8. This cookbook will comprehensively guide you through practical implementation of Tcl/Tk 8.5 commands and tools. This book will take you through all the steps needed to become a productive programmer in Tcl/Tk 8. Right from guiding you through the basics to creating a stand-alone application, it provides complete explanation of all the steps along with handy tips and tricks. The book begins with an introduction to the Tcl shell, syntax, variables, and programming best practices in the language. It then explores procedures and the flow of events with control constructs followed by advanced error trapping and recovery. From Chapter 4, a detailed study of string expressions and handling enables you to handle various string functions and use lists to expand the string functionality. The book then discusses in-depth the Tcl Dictionary and how to utilize it to store and retrieve data. File operations and Tk GUI handling are covered extensively along with a developing a real-world address book application to practice the concepts learned.
Table of Contents (20 chapters)
Tcl/Tk 8.5 Programming Cookbook
About the Author
About the Reviewers

Locating the last instance of a string

To locate the last instance of a string for an exact match, Tcl provides the keyword last. Let's look at the syntax to illustrate how this can be used.

The syntax for the string command is as follows:

string last string1 string2 index

When invoked with the last command, the string command locates the last instance of string1 contained within string2.

How to do it…

In the following example, we locate the last instance of a string contained within another string. Enter the following command:

% string last abc abcabcabc

How it works…

As you can see, string has returned 6, indicating that the last exact match of the search phrase is located at the index of 6. When invoked with the last keyword, the string command searches string1 for a sequence of characters that exactly matches string2. If the match occurs, Tcl returns the index of the first letter of the occurrence. If no match exists, -1 is returned. By passing a numeric value in the index, Tcl will commence...