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

Creating a reverse string

There have been instances in the past where I had the need to reverse the characters I had received from the user input. To assist us in creating a reverse string, Tcl provides the reverse keyword.

The syntax of the string command is as follows:

string reverse string

The string command returns the value stored in string in reverse order.

Getting ready

To complete the following example, we will need to access Tcl from the command line. Launch the Tcl shell appropriately for your operating system and follow the given instructions.

How to do it…

In the following example, we will create a string that is the reverse of the original. Return values from the commands are provided for clarity. Enter the following command:

% string reverse abc

How it works…

Tcl returns a string containing the original string provided in a reverse order.