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 index of a character

What if we need to determine which character exists at a specific location within a string and not just the first instance? To accomplish this, string, includes the index keyword.

The syntax for the string command is as follows:

string index string index

When invoked with the index keyword, the string command returns the character that exists at the location specified in the switch. The accepted values are valid for all the Tcl commands that accept an index and may be passed as follows:



Any integer value

Integer value for a specific index.

Please note that the index is 0-based.


The last character in the string.


The last character in the string minus the numeric offset represented by n.

For example, end-2 would refer to "b" in the string "abcd".


The last character in the string plus the numeric offset represented by n.


The character located at the index, as determined by adding the values of A and B, where A...