![D Programming
10
Example
import std.stdio;
void main(string[] args)
{
writeln("Hello World!");
}
LearningD
The most important thing to do when learning D is to focus on concepts and not get lost in
language technical details.
The purpose of learning a programming language is to become a better programmer; that is,
to become more effective at designing and implementing new systems and at maintaining old
ones.
ScopeofD
D programming has some interesting features and the official D programming site claims that
D is convenient, powerful and efficient. D programming adds many features in the core
language which C language has provided in the form of Standard libraries such as resizable
array and string function. D makes an excellent second language for intermediate to advanced
programmers. D is better in handling memory and managing the pointers that often causes
trouble in C++.
D programming is intended mainly on new programs that conversion of existing programs. It
provides built in testing and verification an ideal for large new project that will be written with
millions of lines of code by large teams.](https://image.slidesharecdn.com/dprogrammingtutorial-180726121223/85/D-programming-tutorial-11-320.jpg)
![D Programming
11
TryitOptionOnline
You really do not need to set up your own environment to start learning D programming
language. Reason is very simple, we already have set up D Programming environment online
under “Try it” option. Using this option, you can build and execute all the given examples
online at the same time when you are learning theory. This gives you confidence in what you
are reading and checking the result with different options. Feel free to modify any example
and execute it online.
Try following example using Try it option available at the top right corner of the below sample
code box:
import std.stdio;
void main(string[] args)
{
writeln("Hello World!");
}
For most of the examples given in this tutorial, you will find Try it option, so just make use
of it and enjoy learning.
LocalEnvironmentSetupforD
If you are still willing to set up your environment for D programming language, you need the
following two softwares available on your computer, (a) Text Editor,(b)D Compiler.
TextEditorforDProgramming
This will be used to type your program. Examples of few editors include Windows Notepad,
OS Edit command, Brief, Epsilon, EMACS, and vim or vi.
Name and version of text editor can vary on different operating systems. For example,
Notepad will be used on Windows, and vim or vi can be used on windows as well as Linux or
UNIX.
The files you create with your editor are called source files and contain program source code.
The source files for D programs are named with the extension ".d".
2. D ─ ENVIRONMENT](https://image.slidesharecdn.com/dprogrammingtutorial-180726121223/85/D-programming-tutorial-12-320.jpg)
![D Programming
12
Before starting your programming, make sure you have one text editor in place and you have
enough experience to write a computer program, save it in a file, build it and finally execute
it.
TheDCompiler
Most current D implementations compile directly into machine code for efficient execution.
We have multiple D compilers available and it includes the following.
DMD - The Digital Mars D compiler is the official D compiler by Walter Bright.
GDC - A front-end for the GCC back-end, built using the open DMD compiler source
code.
LDC - A compiler based on the DMD front-end that uses LLVM as its compiler back-
end.
The above different compilers can be downloaded from D downloads
We will be using D version 2 and we recommend not to download D1.
Let’s have a helloWorld.d program as follows. We will use this as first program we run on
platform you choose.
import std.stdio;
void main(string[] args)
{
writeln("Hello World!");
}
InstallationofDonWindows
Download the windows installer.
Run the downloaded executable to install the D which can be done by following the on screen
instructions.
Now we can build and run a d file say helloWorld.d by switching to folder containing the file
using cd and then using the following steps:
C:DProgramming> DMD helloWorld.d
C:DProgramming> helloWorld
We can see the following output.
hello world](https://image.slidesharecdn.com/dprogrammingtutorial-180726121223/85/D-programming-tutorial-13-320.jpg)
![D Programming
15
D is quite simple to learn and let’s start creating our first D program!
FirstDProgram
Let us write a simple D program. All D files will have extension ".d". So put the following
source code in a test.d file.
import std.stdio;
/* My first program in D */
void main(string[] args)
{
writeln("test!");
}
Assuming D environment is setup correctly, lets run the programming using:
$ dmd test.d
$ ./test
We will get the following output.
test
Let us now see the basic structure of D program, so that it will be easy for you to understand
basic building blocks of the D programming language.
ImportinD
Libraries which are collections of reusable program parts can be made available to our project
with the help of import. Here we import the standard io library which provides the basic I/O
operations. writeln which is used in above program is a function in D's standard library. It is
used for printing a line of text. Library contents in D are grouped into modules which is based
on the types of tasks that they intend perform. The only module that this program uses is
std.stdio, which handles data input and output.
MainFunction
Main function is the starting of the program and it determines the order of execution and how
other sections of the program should be executed.
3. D ─ BASIC SYNTAX](https://image.slidesharecdn.com/dprogrammingtutorial-180726121223/85/D-programming-tutorial-16-320.jpg)
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D programming tutorial
- 2. D Programming i AbouttheTutorial D programming language is an object-oriented multi-paradigm system programming language. D programming is actually developed by re-engineering C++ programming language, but it is distinct programming language that not only takes in some features of C++ but also some features of other programming languages such as Java, C#, Python, and Ruby. This tutorial covers various topics ranging from the basics of the D programming language to advanced OOP concepts along with the supplementary examples. Audience This tutorial is designed for all those individuals who are looking for a starting point of learning D Language. Both beginners and advanced users can refer this tutorial as their learning material. Enthusiastic learners can refer it as their on-the-go reading reference. Any individual with a logical mindset can enjoy learning D through this tutorial. Prerequisites Before proceeding with this tutorial, it is advisable for you to understand the basics concepts of computer programming. You just need to have a basic understanding of working with a simple text editor and command line. Disclaimer&Copyright Copyright 2017 by Tutorials Point (I) Pvt. Ltd. All the content and graphics published in this e-book are the property of Tutorials Point (I) Pvt. Ltd. The user of this e-book is prohibited to reuse, retain, copy, distribute or republish any contents or a part of contents of this e-book in any manner without written consent of the publisher. We strive to update the contents of our website and tutorials as timely and as precisely as possible, however, the contents may contain inaccuracies or errors. Tutorials Point (I) Pvt. Ltd. provides no guarantee regarding the accuracy, timeliness or completeness of our website or its contents including this tutorial. If you discover any errors on our website or in this tutorial, please notify us at [email protected].
- 3. D Programming ii TableofContents About the Tutorial .......................................................................................................................................... i Audience......................................................................................................................................................... i Prerequisites................................................................................................................................................... i Disclaimer & Copyright................................................................................................................................... i Table of Contents........................................................................................................................................... ii PART I - D PROGRAMMING BASICS .............................................................................................1 1. D ─ Overview...........................................................................................................................................2 Multiple Paradigms........................................................................................................................................ 2 Learning D...................................................................................................................................................... 3 Scope of D...................................................................................................................................................... 3 2. D ─ Environment .....................................................................................................................................4 Try it Option Online ....................................................................................................................................... 4 Local Environment Setup for D...................................................................................................................... 4 Text Editor for D Programming...................................................................................................................... 4 The D Compiler .............................................................................................................................................. 5 Installation of D on Windows ........................................................................................................................ 5 Installation of D on Ubuntu/Debian .............................................................................................................. 6 Installation of D on Mac OS X ........................................................................................................................ 6 Installation of D on Fedora ............................................................................................................................ 6 Installation of D on OpenSUSE....................................................................................................................... 7 D IDE .............................................................................................................................................................. 7 3. D ─ Basic Syntax ......................................................................................................................................8 First D Program.............................................................................................................................................. 8 Import in D..................................................................................................................................................... 8 Main Function................................................................................................................................................ 8 Tokens in D .................................................................................................................................................... 9 Comments...................................................................................................................................................... 9 Identifiers....................................................................................................................................................... 9 Keywords ..................................................................................................................................................... 10 Whitespace in D........................................................................................................................................... 11 4. D ─ Variables .........................................................................................................................................12 Variable Definition in D................................................................................................................................ 12 Variable Declaration in D............................................................................................................................. 13 Lvalues and Rvalues in D.............................................................................................................................. 14 5. D ─ Datatypes........................................................................................................................................16 Integer Types ............................................................................................................................................... 16 Floating-Point Types .................................................................................................................................... 18 Character Types........................................................................................................................................... 19 The void Type............................................................................................................................................... 20
- 4. D Programming iii 6. D ─ Enums .............................................................................................................................................21 The enum Syntax ......................................................................................................................................... 21 Named Enums Properties............................................................................................................................ 22 Anonymous Enum........................................................................................................................................ 23 Enum with Base Type Syntax....................................................................................................................... 23 More Features ............................................................................................................................................. 24 7. D ─ Literals ............................................................................................................................................26 Integer Literals............................................................................................................................................. 26 Floating Point Literals .................................................................................................................................. 27 Boolean Literals ........................................................................................................................................... 27 Character Literals......................................................................................................................................... 28 String Literals ............................................................................................................................................... 29 8. D ─ Operators........................................................................................................................................30 Arithmetic Operators................................................................................................................................... 30 Relational Operators.................................................................................................................................... 32 Logical Operators......................................................................................................................................... 34 Bitwise Operators ........................................................................................................................................ 36 Assignment Operators................................................................................................................................. 38 Miscillaneous Operators - Sizeof and Ternary............................................................................................. 41 Operators Precedence in D.......................................................................................................................... 42 9. D ─ Loops ..............................................................................................................................................45 While Loop................................................................................................................................................... 46 for Loop........................................................................................................................................................ 48 Do…While Loop............................................................................................................................................ 50 Nested Loops ............................................................................................................................................... 52 Loop Control Statements............................................................................................................................. 54 Break Statement.......................................................................................................................................... 55 Continue Statement..................................................................................................................................... 56 The Infinite Loop.......................................................................................................................................... 58 10. D ─ Decisions.........................................................................................................................................59 if Statement in D.......................................................................................................................................... 60 if… else Statement ....................................................................................................................................... 61 The if...else if...else Statement..................................................................................................................... 63 Nested if Statements ................................................................................................................................... 65 Switch Statement......................................................................................................................................... 66 Nested Switch Statement ............................................................................................................................ 68 The ? : Operator in D ................................................................................................................................... 70 11. D ─ Functions ........................................................................................................................................71 Function Definition in D............................................................................................................................... 71 Calling a Function......................................................................................................................................... 71 Function Types in D ..................................................................................................................................... 71 Pure Functions............................................................................................................................................. 72 Nothrow Functions...................................................................................................................................... 73 Ref Functions ............................................................................................................................................... 73 Auto Functions............................................................................................................................................. 74
- 5. D Programming iv Variadic Functions ....................................................................................................................................... 75 Inout Functions............................................................................................................................................ 76 Property Functions ...................................................................................................................................... 77 12. D ─ Characters.......................................................................................................................................79 Reading Characters in D............................................................................................................................... 80 13. D ─ Strings.............................................................................................................................................82 Character Array............................................................................................................................................ 82 Core Language String................................................................................................................................... 82 String Concatenation ................................................................................................................................... 83 Length of String ........................................................................................................................................... 84 String Comparison ....................................................................................................................................... 84 Replacing Strings.......................................................................................................................................... 85 Index Methods............................................................................................................................................. 86 Handling Cases............................................................................................................................................. 86 Restricting Characters.................................................................................................................................. 87 14. D ─ Arrays..............................................................................................................................................88 Declaring Arrays........................................................................................................................................... 88 Initializing Arrays ......................................................................................................................................... 88 Accessing Array Elements............................................................................................................................ 89 Static Arrays Versus Dynamic Arrays........................................................................................................... 90 Array Properties........................................................................................................................................... 90 Multi Dimensional Arrays in D..................................................................................................................... 92 Two-Dimensional Arrays in D ...................................................................................................................... 92 Initializing Two-Dimensional Arrays ............................................................................................................ 93 Accessing Two-Dimensional Array Elements............................................................................................... 93 Common Array Operations in D................................................................................................................... 94 15. D ─ Associative Arrays...........................................................................................................................97 Initializing Associative Array ........................................................................................................................ 98 Properties of Associative Array.................................................................................................................... 98 16. D ─ Pointers.........................................................................................................................................101 What Are Pointers? ................................................................................................................................... 101 Using Pointers in D programming.............................................................................................................. 102 Null Pointers .............................................................................................................................................. 103 Pointer Arithmetic ..................................................................................................................................... 103 Incrementing a Pointer.............................................................................................................................. 104 Pointers vs Array........................................................................................................................................ 105 Pointer to Pointer ...................................................................................................................................... 106 Passing Pointer to Functions ..................................................................................................................... 107 Return Pointer from Functions.................................................................................................................. 108 Pointer to an Array .................................................................................................................................... 109
- 6. D Programming v 17. D ─ Tuples ...........................................................................................................................................111 Tuple Using tuple() .................................................................................................................................... 111 Tuple using Tuple Template....................................................................................................................... 111 Expanding Property and Function Params................................................................................................. 112 TypeTuple .................................................................................................................................................. 113 18. D ─ Structures......................................................................................................................................115 Defining a Structure................................................................................................................................... 115 Accessing Structure Members................................................................................................................... 116 Structures as Function Arguments ............................................................................................................ 117 Structs Initialization ................................................................................................................................... 119 Static Members.......................................................................................................................................... 120 19. D ─ Unions...........................................................................................................................................122 Defining a Union in D................................................................................................................................. 122 Accessing Union Members ........................................................................................................................ 123 20. D ─ Ranges ..........................................................................................................................................126 Number ranges .......................................................................................................................................... 126 Phobos Ranges........................................................................................................................................... 126 InputRange ................................................................................................................................................ 126 ForwardRange............................................................................................................................................ 129 BidirectionalRange..................................................................................................................................... 130 Infinite RandomAccessRange .................................................................................................................... 132 Finite RandomAccessRange....................................................................................................................... 134 OutputRange ............................................................................................................................................. 139 21. D ─ Aliases...........................................................................................................................................141 Alias for a Tuple ......................................................................................................................................... 142 Alias for Data Types ................................................................................................................................... 142 Alias for Class Variables ............................................................................................................................. 143 Alias This.................................................................................................................................................... 144 22. D ─ Mixins ...........................................................................................................................................146 String Mixins .............................................................................................................................................. 146 Template Mixins ........................................................................................................................................ 147 Mixin Name Spaces.................................................................................................................................... 148 23. D ─ Modules........................................................................................................................................150 File and Module Names............................................................................................................................. 150 D Packages................................................................................................................................................. 151 Using Modules in Programs....................................................................................................................... 151 Locations of Modules ................................................................................................................................ 152 Long and Short Module Names ................................................................................................................. 152
- 7. D Programming vi 24. D ─ Templates .....................................................................................................................................155 Function Template..................................................................................................................................... 155 Function Template with Multiple Type Parameters.................................................................................. 156 Class Templates ......................................................................................................................................... 156 25. D ─ Immutables...................................................................................................................................159 Types of Immutable Variables in D............................................................................................................ 159 enum Constants in D.................................................................................................................................. 159 Immutable Variables in D .......................................................................................................................... 160 Const Variables in D................................................................................................................................... 161 Immutable Parameters in D....................................................................................................................... 162 26. D ─ File I/O ..........................................................................................................................................163 Opening Files in D ...................................................................................................................................... 163 Closing a File in D....................................................................................................................................... 164 Writing a File in D ...................................................................................................................................... 164 Reading a File in D ..................................................................................................................................... 164 27. D ─ Concurrency..................................................................................................................................167 Initiating Threads in D................................................................................................................................ 167 Thread Identifiers in D ............................................................................................................................... 168 Message Passing in D................................................................................................................................. 169 Message Passing with Wait in D ................................................................................................................ 171 28. D ─ Exception Handling .......................................................................................................................173 Throwing Exceptions in D .......................................................................................................................... 174 Catching Exceptions in D............................................................................................................................ 174 29. D ─ Contract Programming..................................................................................................................177 Body Block in D .......................................................................................................................................... 177 In Block for Pre Conditions in D ................................................................................................................. 177 Out Blocks for Post Conditions in D........................................................................................................... 178 30. D ─ Conditional Compilation................................................................................................................180 Debug Statement in D ............................................................................................................................... 180 Debug (tag) Statement in D ....................................................................................................................... 181 Debug (level) Statement in D..................................................................................................................... 181 Version (tag) and Version (level) Statements in D..................................................................................... 182 Static if....................................................................................................................................................... 182 PART II – OBJECT ORIENTED D.................................................................................................184 31. D ─ Classes and Objects.......................................................................................................................185 D Class Definitions ..................................................................................................................................... 185 Defining D Objects ..................................................................................................................................... 185 Accessing the Data Members .................................................................................................................... 186 Classes and Objects in D ............................................................................................................................ 187 Class Member Functions in D .................................................................................................................... 188 Class Access Modifiers in D........................................................................................................................ 189 The Public Members in D........................................................................................................................... 190
- 8. D Programming vii The Private Members ................................................................................................................................ 191 The Protected Members............................................................................................................................ 193 The Class Constructor................................................................................................................................ 194 Parameterized Constructor ....................................................................................................................... 195 The Class Destructor.................................................................................................................................. 196 this Pointer in D ......................................................................................................................................... 198 Pointer to D Classes................................................................................................................................... 199 Static Members of a Class.......................................................................................................................... 201 Static Function Members........................................................................................................................... 202 32. D ─ Inheritance....................................................................................................................................205 Base Classes and Derived Classes in D....................................................................................................... 205 Access Control and Inheritance ................................................................................................................. 206 Multi Level Inheritance.............................................................................................................................. 207 33. D ─ Overloading ..................................................................................................................................209 Function Overloading ................................................................................................................................ 209 Operator Overloading................................................................................................................................ 210 Operator Overloading Types ..................................................................................................................... 213 Unary Operators........................................................................................................................................ 213 Binary Operators........................................................................................................................................ 216 Comparison of Operator Overloading ....................................................................................................... 219 34. D ─ Encapsulation................................................................................................................................222 Data Encapsulation in D............................................................................................................................. 223 Class Designing Strategy in D..................................................................................................................... 224 35. D ─ Interfaces......................................................................................................................................225 Interface with Final and Static Functions in D ........................................................................................... 226 36. D ─ Abstract Classes ............................................................................................................................229 Using Abstract Class in D ........................................................................................................................... 229 Abstract Functions..................................................................................................................................... 230
- 9. D Programming 8 Part I - D Programming Basics
- 10. D Programming 9 D programming language is an object-oriented multi-paradigm system programming language developed by Walter Bright of Digital Mars. Its development started in 1999 and was first released in 2001. The major version of D(1.0) was released in 2007. Currently, we have D2 version of D. D is language with syntax being C style and uses static typing. There are many features of C and C++ in D but also there are some features from these language not included part of D. Some of the notable additions to D includes, Unit testing True modules Garbage collection First class arrays Free and open Associative arrays Dynamic arrays Inner classes Closures Anonymous functions Lazy evaluation Closures MultipleParadigms D is a multiple paradigm programming language. The multiple paradigms includes, Imperative Object Oriented Meta programming Functional Concurrent 1. D ─ OVERVIEW
- 11. D Programming 10 Example import std.stdio; void main(string[] args) { writeln("Hello World!"); } LearningD The most important thing to do when learning D is to focus on concepts and not get lost in language technical details. The purpose of learning a programming language is to become a better programmer; that is, to become more effective at designing and implementing new systems and at maintaining old ones. ScopeofD D programming has some interesting features and the official D programming site claims that D is convenient, powerful and efficient. D programming adds many features in the core language which C language has provided in the form of Standard libraries such as resizable array and string function. D makes an excellent second language for intermediate to advanced programmers. D is better in handling memory and managing the pointers that often causes trouble in C++. D programming is intended mainly on new programs that conversion of existing programs. It provides built in testing and verification an ideal for large new project that will be written with millions of lines of code by large teams.
- 12. D Programming 11 TryitOptionOnline You really do not need to set up your own environment to start learning D programming language. Reason is very simple, we already have set up D Programming environment online under “Try it” option. Using this option, you can build and execute all the given examples online at the same time when you are learning theory. This gives you confidence in what you are reading and checking the result with different options. Feel free to modify any example and execute it online. Try following example using Try it option available at the top right corner of the below sample code box: import std.stdio; void main(string[] args) { writeln("Hello World!"); } For most of the examples given in this tutorial, you will find Try it option, so just make use of it and enjoy learning. LocalEnvironmentSetupforD If you are still willing to set up your environment for D programming language, you need the following two softwares available on your computer, (a) Text Editor,(b)D Compiler. TextEditorforDProgramming This will be used to type your program. Examples of few editors include Windows Notepad, OS Edit command, Brief, Epsilon, EMACS, and vim or vi. Name and version of text editor can vary on different operating systems. For example, Notepad will be used on Windows, and vim or vi can be used on windows as well as Linux or UNIX. The files you create with your editor are called source files and contain program source code. The source files for D programs are named with the extension ".d". 2. D ─ ENVIRONMENT
- 13. D Programming 12 Before starting your programming, make sure you have one text editor in place and you have enough experience to write a computer program, save it in a file, build it and finally execute it. TheDCompiler Most current D implementations compile directly into machine code for efficient execution. We have multiple D compilers available and it includes the following. DMD - The Digital Mars D compiler is the official D compiler by Walter Bright. GDC - A front-end for the GCC back-end, built using the open DMD compiler source code. LDC - A compiler based on the DMD front-end that uses LLVM as its compiler back- end. The above different compilers can be downloaded from D downloads We will be using D version 2 and we recommend not to download D1. Let’s have a helloWorld.d program as follows. We will use this as first program we run on platform you choose. import std.stdio; void main(string[] args) { writeln("Hello World!"); } InstallationofDonWindows Download the windows installer. Run the downloaded executable to install the D which can be done by following the on screen instructions. Now we can build and run a d file say helloWorld.d by switching to folder containing the file using cd and then using the following steps: C:DProgramming> DMD helloWorld.d C:DProgramming> helloWorld We can see the following output. hello world
- 14. D Programming 13 C:DProgramming is the folder, I am using to save my samples. You can change it to the folder that you have saved D programs. InstallationofDonUbuntu/Debian Download the debian installer. Run the downloaded executable to install the D which can be done by following the on screen instructions. Now we can build and run a d file say helloWorld.d by switching to folder containing the file using cd and then using the following steps $ dmd helloWorld.d $ ./helloWorld We can see the following output. $ hello world InstallationofDonMacOSX Download the Mac installer. Run the downloaded executable to install the D which can be done by following the on screen instructions. Now we can build and run a d file say helloWorld.d by switching to folder containing the file using cd and then using the following steps $ dmd helloWorld.d $ ./helloWorld We can see the following output. $ hello world InstallationofDonFedora Download the fedora installer. Run the downloaded executable to install the D which can be done by following the on screen instructions. Now we can build and run a d file say helloWorld.d by switching to folder containing the file using cd and then using the following steps:
- 15. D Programming 14 $ dmd helloWorld.d $ ./helloWorld We can see the following output. $ hello world InstallationofDonOpenSUSE Download the OpenSUSE installer. Run the downloaded executable to install the D which can be done by following the on screen instructions. Now we can build and run a d file say helloWorld.d by switching to folder containing the file using cd and then using the following steps $ dmd helloWorld.d $ ./helloWorld We can see the following output. $ hello world DIDE We have IDE support for D in the form of plugins in most cases. This includes, Visual D plugin is a plugin for Visual Studio 2005-13 DDT is a eclipse plugin that provides code completion, debugging with GDB. Mono-D code completion, refactoring with dmd/ldc/gdc support. It has been part of GSoC 2012. Code Blocks is a multi-platform IDE that supports D project creation, highlighting and debugging.
- 16. D Programming 15 D is quite simple to learn and let’s start creating our first D program! FirstDProgram Let us write a simple D program. All D files will have extension ".d". So put the following source code in a test.d file. import std.stdio; /* My first program in D */ void main(string[] args) { writeln("test!"); } Assuming D environment is setup correctly, lets run the programming using: $ dmd test.d $ ./test We will get the following output. test Let us now see the basic structure of D program, so that it will be easy for you to understand basic building blocks of the D programming language. ImportinD Libraries which are collections of reusable program parts can be made available to our project with the help of import. Here we import the standard io library which provides the basic I/O operations. writeln which is used in above program is a function in D's standard library. It is used for printing a line of text. Library contents in D are grouped into modules which is based on the types of tasks that they intend perform. The only module that this program uses is std.stdio, which handles data input and output. MainFunction Main function is the starting of the program and it determines the order of execution and how other sections of the program should be executed. 3. D ─ BASIC SYNTAX
- 17. D Programming 16 TokensinD A D program consists of various tokens and a token is either a keyword, an identifier, a constant, a string literal, or a symbol. For example, the following D statement consists of four tokens: writeln("test!"); The individual tokens are: writeln ( "test!" ) ; Comments Comments are like supporting text in your D program and they are ignored by the compiler. Multi line comment starts with /* and terminates with the characters */ as shown below: /* My first program in D */ Single comment is written using // in the beginning of the comment. // my first program in D Identifiers A D identifier is a name used to identify a variable, function, or any other user-defined item. An identifier starts with a letter A to Z or a to z or an underscore _ followed by zero or more letters, underscores, and digits (0 to 9). D does not allow punctuation characters such as @, $, and % within identifiers. D is a case sensitive programming language. Thus Manpower and manpower are two different identifiers in D. Here are some examples of acceptable identifiers: mohd zara abc move_name a_123 myname50 _temp j a23b9 retVal
- 18. D Programming 17 Keywords The following list shows few of the reserved words in D. These reserved words may not be used as constant or variable or any other identifier names. abstract alias align asm assert auto body bool byte case cast catch char class const continue dchar debug default delegate deprecated do double else enum export extern false final finally float for foreach function goto if import in inout int interface invariant is long macro mixin module new null out override package pragma private protected public real ref return scope short static struct super switch synchronized template this
- 19. D Programming 18 throw true try typeid typeof ubyte uint ulong union unittest ushort version void wchar while with WhitespaceinD A line containing only whitespace, possibly with a comment, is known as a blank line, and a D compiler totally ignores it. Whitespace is the term used in D to describe blanks, tabs, newline characters and comments. Whitespace separates one part of a statement from another and enables the interpreter to identify where one element in a statement, such as int, ends and the next element begins. Therefore, in the following statement: local age There must be at least one whitespace character (usually a space) between local and age for the interpreter to be able to distinguish them. On the other hand, in the following statement int fruit = apples + oranges //get the total fruits No whitespace characters are necessary between fruit and =, or between = and apples, although you are free to include some if you wish for readability purpose.
- 20. D Programming 19 A variable is nothing but a name given to a storage area that our programs can manipulate. Each variable in D has a specific type, which determines the size and layout of the variable's memory; the range of values that can be stored within that memory; and the set of operations that can be applied to the variable. The name of a variable can be composed of letters, digits, and the underscore character. It must begin with either a letter or an underscore. Upper and lowercase letters are distinct because D is case-sensitive. Based on the basic types explained in the previous chapter, there will be the following basic variable types: Type Description char Typically a single octet (one byte). This is an integer type. int The most natural size of integer for the machine. float A single-precision floating point value. double A double-precision floating point value. void Represents the absence of type. D programming language also allows to define various other types of variables such as Enumeration, Pointer, Array, Structure, Union, etc., which we will cover in subsequent chapters. For this chapter, let us study only basic variable types. VariableDefinitioninD A variable definition tells the compiler where and how much space to create for the variable. A variable definition specifies a data type and contains a list of one or more variables of that type as follows: type variable_list; Here, type must be a valid D data type including char, wchar, int, float, double, bool, or any user-defined object, etc., and variable_list may consist of one or more identifier names separated by commas. Some valid declarations are shown here: 4. D ─ VARIABLES
- 21. D Programming 20 int i, j, k; char c, ch; float f, salary; double d; The line int i, j, k; both declares and defines the variables i, j and k; which instructs the compiler to create variables named i, j, and k of type int. Variables can be initialized (assigned an initial value) in their declaration. The initializer consists of an equal sign followed by a constant expression as follows: type variable_name = value; Example extern int d = 3, f = 5; // declaration of d and f. int d = 3, f = 5; // definition and initializing d and f. byte z = 22; // definition and initializes z. char x = 'x'; // the variable x has the value 'x'. When a variable is declared in D, it is always set to its 'default initializer', which can be manually accessed as T.init where T is the type (ex. int.init). The default initializer for integer types is 0, for Booleans false, and for floating-point numbers NaN. VariableDeclarationinD A variable declaration provides assurance to the compiler that there is one variable existing with the given type and name so that compiler proceed for further compilation without needing complete detail about the variable. A variable declaration has its meaning at the time of compilation only, compiler needs actual variable declaration at the time of linking of the program. Example Try the following example, where variables have been declared at the start of the program, but are defined and initialized inside the main function: import std.stdio; int a = 10, b =10; int c; float f;
- 22. D Programming 21 int main () { writeln("Value of a is : ", a); /* variable re definition: */ int a, b; int c; float f; /* Initialization */ a = 30; b = 40; writeln("Value of a is : ", a); c = a + b; writeln("Value of c is : ", c); f = 70.0/3.0; writeln("Value of f is : ", f); return 0; } When the above code is compiled and executed, it produces the following result: Value of a is : 10 Value of a is : 30 Value of c is : 70 Value of f is : 23.3333 LvaluesandRvaluesinD There are two kinds of expressions in D: lvalue : An expression that is an lvalue may appear as either the left-hand or right- hand side of an assignment. rvalue : An expression that is an rvalue may appear on the right- but not left-hand side of an assignment. Variables are lvalues and so may appear on the left-hand side of an assignment. Numeric literals are rvalues and so may not be assigned and cannot appear on the left-hand side.
- 23. D Programming 22 The following statement is valid: int g = 20; But the following is not a valid statement and would generate a compile-time error: 10 = 20;
- 24. D Programming 23 In the D programming language, data types refer to an extensive system used for declaring variables or functions of different types. The type of a variable determines how much space it occupies in storage and how the stored bit pattern is interpreted. The types in D can be classified as follows: Sr. No. Types and Description 1 Basic Types: They are arithmetic types and consist of the three types: (a) integer, (b) floating-point, and (c) character. 2 Enumerated types: They are again arithmetic types. They are used to define variables that can only be assigned certain discrete integer values throughout the program. 3 The type void: The type specifier void indicates that no value is available. 4 Derived types: They include (a) Pointer types, (b) Array types, (c) Structure types, (d) Union types, and (e) Function types. The array types and structure types are referred to collectively as the aggregate types. The type of a function specifies the type of the function's return value. We will see basic types in the following section whereas other types will be covered in the upcoming chapters. IntegerTypes The following table gives lists standard integer types with their storage sizes and value ranges: Type Storage size Value range bool 1 byte false or true 5. D ─ DATATYPES
- 25. D Programming 24 byte 1 byte -128 to 127 ubyte 1 byte 0 to 255 int 4 bytes -2,147,483,648 to 2,147,483,647 uint 4 bytes 0 to 4,294,967,295 short 2 bytes -32,768 to 32,767 ushort 2 bytes 0 to 65,535 long 8 bytes -9223372036854775808 to 9223372036854775807 ulong 8 bytes 0 to 18446744073709551615 To get the exact size of a type or a variable, you can use the sizeof operator. The expression type.(sizeof) yields the storage size of the object or type in bytes. The following example gets the size of int type on any machine: import std.stdio; int main() { writeln("Length in bytes: ", ulong.sizeof); return 0; } When you compile and execute the above program, it produces the following result: Length in bytes: 8
- 26. D Programming 25 Floating-PointTypes The following table mentions standard float-point types with storage sizes, value ranges, and their purpose: Type Storage size Value range Purpose float 4 bytes 1.17549e-38 to 3.40282e+38 6 decimal places double 8 bytes 2.22507e-308 to 1.79769e+308 15 decimal places real 10 bytes 3.3621e-4932 to 1.18973e+4932 either the largest floating point type that the hardware supports, or double; whichever is larger ifloat 4 bytes 1.17549e-38i to 3.40282e+38i imaginary value type of float idouble 8 bytes 2.22507e-308i to 1.79769e+308i imaginary value type of double ireal 10 bytes 3.3621e-4932 to 1.18973e+4932 imaginary value type of real cfloat 8 bytes 1.17549e-38+1.17549e-38i to 3.40282e+38+3.40282e+38i complex number type made of two floats cdouble 16 bytes 2.22507e-308+2.22507e-308i to 1.79769e+308+1.79769e+308i complex number type made of two doubles creal 20 bytes 3.3621e-4932+3.3621e-4932i to 1.18973e+4932+1.18973e+4932i complex number type made of two reals
- 27. D Programming 26 The following example prints storage space taken by a float type and its range values: import std.stdio; int main() { writeln("Length in bytes: ", float.sizeof); return 0; } When you compile and execute the above program, it produces the following result on Linux: Storage size for float : 4 CharacterTypes The following table lists standard character types with storage sizes and its purpose. Type Storage size Purpose char 1 byte UTF-8 code unit wchar 2 bytes UTF-16 code unit dchar 4 bytes UTF-32 code unit and Unicode code point The following example prints storage space taken by a char type. import std.stdio; int main() { writeln("Length in bytes: ", char.sizeof); return 0; } When you compile and execute the above program, it produces the following result: Storage size for float : 1
- 28. D Programming 27 ThevoidType The void type specifies that no value is available. It is used in two kinds of situations: Sr. No. Types and Description 1 Function returns as void There are various functions in D which do not return value or you can say they return void. A function with no return value has the return type as void. For example, void exit (int status); 2 Function arguments as void There are various functions in D which do not accept any parameter. A function with no parameter can accept as a void. For example, int rand(void); The void type may not be understood to you at this point, so let us proceed and we will cover these concepts in upcoming chapters.
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