• Introduction
• Lexical
• Interpolation Expression Sequence
• Grammar
• Modules
• Declarations
• Types
• Properties
• Attributes
• Pragmas
• Expressions
• Statements
• Arrays
• Associative Arrays
• Structs and Unions
• Classes
• Interfaces
• Enums
• Type Qualifiers
• Functions
• Operator Overloading
• Templates
• Template Mixins
• Contract Programming
• Conditional Compilation
• Traits
• Error Handling
• Unit Tests
• Garbage Collection
• Floating Point
• D x86 Inline Assembler
• Embedded Documentation
• Interfacing to C
• Interfacing to C++
• Interfacing to Objective-C
• Portability Guide
• Named Character Entities
• Memory Safety
• Application Binary Interface
• Vector Extensions
• Better C
• ImportC
• Live Functions
• Windows Programming
• Glossary
• Legacy Code
• Editions

Introduction

D is a general-purpose systems programming language with a C-like syntax that compiles to native code.It is statically typed and supports both automatic (garbage collected) and manual memory management.D programs are structured as modules that can be compiled separately and linked with external librariesto create native libraries or executables.

This document is the reference manual for the D Programming Language. For more information andother documents, seeThe D Language Website.

Phases of Compilation

The process of compiling is divided into multiple phases. Each phase isindependent of subsequent phases. For example, the scanner is not affected bythe semantic analyzer. This separation of passes makes language tools likesyntax-directed editors relatively easy to create.

1. source character set
   
   The source file is checked to determine its encoding and the appropriate scanner is loaded. 7-bit ASCII and UTF encodings are accepted.
2. script line
   
   If the first line starts with "#!", then that line is ignored.
3. lexical analysis
   
   The source file is divided into a sequence of tokens.Special tokens are replaced with other tokens.SpecialTokenSequences are processed and removed.
4. syntax analysis
   
   The sequence of tokens is parsed to form syntax trees.
5. semantic analysis
   
   The syntax trees are traversed to declare variables, load symbol tables, assign types, and determine the meaning of the program.
6. optimization
   
   Optimization is an optional pass that attempts to rewrite the program in a semantically equivalent, more performant, version.
7. code generation
   
   Instructions are selected from the target architecture to implement the semantics of the program. The typical result will be an object file suitable for input to a linker.

Memory Model

Thebyte is the fundamental unit of storage. Each byte has 8 bits and is stored at a unique address. Amemory location is a sequence of one or more bytes of the exact size required to hold a scalar type. Multiple threads can access separate memory locations without interference.

Memory locations come in three groups:

1. Thread-local memory locations are accessible from only one thread at a time.
2. Immutable memory locations cannot be written to during their lifetime. Immutable memory locations can be read from by multiple threads without synchronization.
3. Shared memory locations are accessible from multiple threads.

Execution of a single thread on thread-local and immutable memory locations issequentially consistent. This means the collective result of the operations is the same as if they were executed in the same order that the operations appear in the program.

A memory location can be transferred from thread-local to immutable or shared if there is only one reference to the location.

A memory location can be transferred from shared to immutable or thread-local if there is only one reference to the location.

A memory location can be temporarily transferred from shared to local if synchronization is used to prevent any other threads from accessing the memory location during the operation.

Object Model

Anobject is created in the following circumstances:

• a definition
• aNewExpression
• a temporary is created
• changing which field of a union is active

An object spans a sequence of memory locations which may or may not be contiguous. Its lifetime encompasses construction, destruction, and the period in between. Each object has a type which is determined either statically or by runtime type information. The object's memory locations may include any combination of thread-local, immutable, or shared.

Objects can be composed into acomposed object. Objects that make up a composed object aresubobjects. An object that is not the subobject of another object is acomplete object. The lifetime of a subobject is always within the lifetime of the complete object to which it belongs.

An object's address is the address of the first byte of the first memory location for that object. Object addresses are distinct unless one object is nested within the other.

Arithmetic

Integer Arithmetic

Integer arithmetic is performed usingtwo's complement math. Integer overflow is not checked for.

Floating Point Arithmetic

Floating point arithmetic is performed usingIEEE-754 floating point math.