Tcl/Tk 8.5 Programming Cookbook

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.

Tcl/Tk 8.5 Programming Cookbook

Credits

About the Author

Acknowledgment

About the Reviewers

www.PacktPub.com

Preface

Free Chapter

The Tcl Shell

Introduction

The Tcl shell

Writing to the Tcl console

Mathematical expressions

Tcl expr operands

Mathematical functions

Computing mathematical expressions

Referencing files in Tcl

Variables

Command line arguments

Using the Building Blocks Control Constructs

Introduction

Controlling flow with the if statement

Looping with for

Looping with foreach

Looping with while

Continuing a procedure

Breaking out of a procedure

Nested looping

Error Handling

Introduction

Using the catch command

Using the eval command

Using the error command

Error handling procedure

Handling String Expressions

Introduction

Appending to a string

Formatting a string

Matching a regular expression within a string

Performing character substitution on a string

Parsing a string using conversion specifiers

Determining the length of a string

Comparing strings

Comparing a string of characters

Locating the first instance of a character

Locating the index of a character

Determining the class of a string

Locating the last instance of a string

Determining the size of a string

Replacing values within a string

Locating a pattern within a string

Returning a range of characters from a string

Creating a string of repeated characters

Replacing ranges of characters contained within a string

Creating a reverse string

Converting a string to lowercase

Converting a string to title

Converting a string to uppercase

Trimming a string

Trimming leading whitespace

Trimming trailing whitespace

Locating the word end

Locating the word start

Performing variable substitution

Expanding String Functionality Using Lists

Introduction

Creating a list

Joining two lists

Joining list elements

Appending list elements

Assigning list elements to variables

Retrieving an element from a list

Inserting elements into a list

Determining the number of elements

Getting a list element

Splitting a string into a list

The Tcl Dictionary

Introduction

Creating a dictionary

Appending to a dictionary

Determining if a key exists

Filtering a dictionary

Searching a dictionary

Getting a record

Incrementing a value

Getting the dictionary structure

Getting a list of keys

Appending to an existing record

Merging two dictionaries

Creating a blank dictionary structure

Updating variables from a dictionary

Determining the size of a dictionary

File Operations

Opening a command pipeline

Tk GUI Programming with Tcl/Tk

Introduction

Creating a widget

Writing to the console

Setting the attributes of the window through window manager

Creating an additional window

Configuring and Controlling Tk Widgets

Introduction

Creating a frame widget

Creating a label widget

Creating an entry widget

Creating a button widget

Creating a listbox widget

Creating an image

Creating a simple form

Geometry Management

Introduction

Controlling layout with the pack command

Controlling layout with the grid command

Combining pack and grid

Creating an address book interface

Using Tcl Built-in Dialog Windows

Introduction

Displaying a message box

Displaying a confirmation dialog

Displaying the color picker

Displaying the directory dialog

Displaying the file selection dialog

Selecting a directory and file

Creating and Managing Menus

Introduction

Creating a menu

Adding menu buttons

Displaying a pop-up menu

Data entry application

Creating the Address Book Application

Introduction

Creating the Address Book application

Customer Reviews

5 star

4 star

3 star

2 star

1 star

Mathematical functions

Mathematical functions (such as sine and cosine) are replaced with a call to the Tcl mathfunc namespace. This does not require any additional syntax to access the namespace as it is called automatically. These are invoked by passing the Function followed by the value or values to evaluate to the expr command. Those functions that accept multiple arguments require that the arguments be comma delimited. The default Mathematical functions are listed below in alphabetical order. These functions require a specific syntax (for example expr {function(value,value)}) to be accessed, as described in the Computing mathematical expressions section that follows:

Function	Result
`abs arg`	Returns the absolute value of `arg`. Numeric operators may be integer or floating-point. Value is returned in the same format.
`acos arg`	Returns the arc cosine of `arg.`
`asin arg`	Returns the arc sine of `arg.`
`atan arg`	Returns the Arc Tangent of x/y.
`bool arg`	Returns the Boolean value of `arg` where non-numeric values are `true`, otherwise the value is `false.`
`ceil arg`	Returns the smallest floating-point integer value not less than `arg.` Any numeric value is acceptable.
`cos arg`	Returns the cosine of `arg`, measured in radians. If the result produces an over-flow, an error is returned.
`double arg`	Converts `arg` to its floating-point value. May return INF or INF when the numeric value is such that it exceeds the floating-point value.
`entier arg`	Converts `arg` to its integer value.
`exp arg`	Returns the exponential of `arg`. If the result produces an over-flow, an error is returned.
`floor arg`	Returns the largest floating-point integer not greater than `arg`. The argument may be any numeric value.
`fmod x y`	Returns the remainder of `x/y` as a floating-point integer. If `y` is a zero (0), then an error is returned.
`hypot x y`	Returns the length of the hypotenuse of a right angled triangle.
`int arg`	Returns the low order bits of `arg` up to the machine word size.
`isqrt arg`	Returns the integer portion of the square root of `arg`. Arg must be a positive value (integer or floating-point).
`log arg`	Returns the natural logarithm of `arg`. `arg` must be a positive value.
`log10 arg`	Returns the base 10 logarithm of `arg`. `arg` must be a positive value.
`max arg`	This function accepts one or more numeric values and returns the greatest.
`min arg`	This function accepts one or more numeric and returns the least one.
`pow x y`	Returns the value of `x` raised to the power `y`. If `x` is zero (0), `y` must be an integer value.
`rand`	Returns a pseudo-random floating-point integer in the range of 0, 1.
`round arg`	Returns the rounded value of `arg` if `arg` is an integer value. If `arg` is not an integer, it is converted to an integer by rounding and the converted value is returned.
`sin arg`	Returns the sine of `arg` as radians.
`sinh arg`	Returns the hyperbolic sin of `arg.` If the result produces an over-flow, an error is returned.
`sqrt arg`	Returns the square root of `arg`. Accepts any non-negative numeric value. May return INF when the value is a numeric value that exceeds the square of the maximum value for the floating-point range.
`srand arg`	Resets the seed for the random number generator and returns a random number as described in `rand`.
`tan arg`	Returns the tangent of `arg` as radians.
`tanh arg`	Returns the hyperbolic tangent of `arg`.
`wide arg`	Returns the low order 64 bits of `arg`. Accepts any numeric value.

Tcl/Tk 8.5 Programming Cookbook

Tcl/Tk 8.5 Programming Cookbook

Overview of this book

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Tcl/Tk 8.5 Programming Cookbook

Mathematical functions