OPLG.pdf

Object Pascal

Language Guide

Borland ®

Object Pascal

Borland Software Corporation

100 Enterprise Way, Scotts Valley, CA 95066-3249

www.borland.com

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ALP0000WW21000 1E0R0501

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Contents

Chapter 1

Introduction 1-1

What’s in this manual? . . . . . . . . . . . . . . 1-1

Using Object Pascal . . . . . . . . . . . . . . 1-1

Typographical conventions . . . . . . . . . . 1-2

Other sources of information . . . . . . . . . . . 1-2

Software registration and technical support . . 1-3

Reserved words . . . . . . . . . . . . . . . . . 4-3

Directives. . . . . . . . . . . . . . . . . . . . . 4-3

Numerals . . . . . . . . . . . . . . . . . . . . . 4-4

Labels . . . . . . . . . . . . . . . . . . . . . . . 4-4

Character strings . . . . . . . . . . . . . . . . 4-4

Comments and compiler directives . . . . . . . . 4-5

Expressions . . . . . . . . . . . . . . . . . . . . . 4-5

Operators. . . . . . . . . . . . . . . . . . . . . 4-6

Arithmetic operators . . . . . . . . . . . . 4-6

Boolean operators . . . . . . . . . . . . . . 4-7

Logical (bitwise) operators . . . . . . . . . 4-8

String operators . . . . . . . . . . . . . . . 4-9

Pointer operators. . . . . . . . . . . . . . . 4-9

Set operators . . . . . . . . . . . . . . . . 4-10

Relational operators . . . . . . . . . . . . 4-10

Class operators . . . . . . . . . . . . . . . 4-11

The @ operator . . . . . . . . . . . . . . . 4-12

Operator precedence rules . . . . . . . . 4-12

Function calls . . . . . . . . . . . . . . . . . 4-13

Set constructors . . . . . . . . . . . . . . . . 4-13

Indexes . . . . . . . . . . . . . . . . . . . . . 4-14

Typecasts . . . . . . . . . . . . . . . . . . . . 4-14

Value typecasts . . . . . . . . . . . . . . . 4-14

Variable typecasts . . . . . . . . . . . . . 4-15

Declarations and statements . . . . . . . . . . . 4-16

Declarations . . . . . . . . . . . . . . . . . . 4-16

Statements . . . . . . . . . . . . . . . . . . . 4-17

Simple statements . . . . . . . . . . . . . . . 4-17

Assignment statements . . . . . . . . . . 4-17

Procedure and function calls . . . . . . . 4-18

Goto statements . . . . . . . . . . . . . . 4-18

Structured statements . . . . . . . . . . . . . 4-19

Compound statements . . . . . . . . . . 4-20

With statements . . . . . . . . . . . . . . 4-20

If statements . . . . . . . . . . . . . . . . 4-22

Case statements . . . . . . . . . . . . . . 4-23

Control loops . . . . . . . . . . . . . . . . 4-25

Repeat statements . . . . . . . . . . . . . 4-25

While statements. . . . . . . . . . . . . . 4-25

For statements . . . . . . . . . . . . . . . 4-26

Blocks and scope . . . . . . . . . . . . . . . . . 4-27

Blocks . . . . . . . . . . . . . . . . . . . . . . 4-27

Scope . . . . . . . . . . . . . . . . . . . . . . 4-28

Naming conflicts . . . . . . . . . . . . . . 4-29

Part I

Basic language description

Chapter 2

Overview 2-1

Program organization . . . . . . . . . . . . . . . 2-1

Pascal source files . . . . . . . . . . . . . . . 2-1

Other files used to build applications . . . . 2-2

Compiler-generated files . . . . . . . . . . . 2-3

Example programs. . . . . . . . . . . . . . . . . 2-3

A simple console application . . . . . . . . . 2-3

A more complicated example . . . . . . . . . 2-4

A native application . . . . . . . . . . . . . . 2-5

Chapter 3

Programs and units 3-1

Program structure and syntax . . . . . . . . . . 3-1

The program heading . . . . . . . . . . . . . 3-2

The program uses clause . . . . . . . . . . . 3-2

The block . . . . . . . . . . . . . . . . . . . . 3-2

Unit structure and syntax . . . . . . . . . . . . . 3-3

The unit heading . . . . . . . . . . . . . . . . 3-3

The interface section . . . . . . . . . . . . . . 3-4

The implementation section. . . . . . . . . . 3-4

The initialization section. . . . . . . . . . . . 3-4

The finalization section . . . . . . . . . . . . 3-5

Unit references and the uses clause . . . . . . . 3-5

The syntax of a uses clause . . . . . . . . . . 3-6

Multiple and indirect unit references . . . . 3-6

Circular unit references . . . . . . . . . . . . 3-7

Chapter 4

Syntactic elements 4-1

Fundamental syntactic elements . . . . . . . . . 4-1

Special symbols . . . . . . . . . . . . . . . . . 4-2

Identifiers . . . . . . . . . . . . . . . . . . . . 4-2

Qualified identifiers . . . . . . . . . . . . 4-2

iii

Chapter 5

Data types, variables, and constants 5-1

About types. . . . . . . . . . . . . . . . . . . . . 5-1

Simple types . . . . . . . . . . . . . . . . . . . . 5-2

Ordinal types . . . . . . . . . . . . . . . . . . 5-2

Integer types. . . . . . . . . . . . . . . . . 5-3

Character types . . . . . . . . . . . . . . . 5-5

Boolean types . . . . . . . . . . . . . . . . 5-5

Enumerated types . . . . . . . . . . . . . 5-6

Subrange types . . . . . . . . . . . . . . . 5-8

Real types . . . . . . . . . . . . . . . . . . . . 5-9

String types . . . . . . . . . . . . . . . . . . . . . 5-10

Short strings. . . . . . . . . . . . . . . . . . . 5-12

Long strings . . . . . . . . . . . . . . . . . . . 5-12

WideString . . . . . . . . . . . . . . . . . . . 5-13

About extended character sets . . . . . . 5-13

Working with null-terminated strings . . . . 5-13

Using pointers, arrays, and string

constants . . . . . . . . . . . . . . . . . . 5-14

Mixing Pascal strings and

null-terminated strings . . . . . . . . . . 5-15

Structured types . . . . . . . . . . . . . . . . . . 5-16

Sets . . . . . . . . . . . . . . . . . . . . . . . . 5-17

Arrays . . . . . . . . . . . . . . . . . . . . . . 5-18

Static arrays . . . . . . . . . . . . . . . . . 5-18

Dynamic arrays . . . . . . . . . . . . . . . 5-19

Array types and assignments . . . . . . . 5-21

Records . . . . . . . . . . . . . . . . . . . . . 5-21

Variant parts in records . . . . . . . . . . 5-22

File types . . . . . . . . . . . . . . . . . . . . 5-24

Pointers and pointer types . . . . . . . . . . . . 5-25

Overview of pointers . . . . . . . . . . . . . 5-25

Pointer types . . . . . . . . . . . . . . . . . . 5-27

Character pointers . . . . . . . . . . . . . 5-27

Other standard pointer types . . . . . . . 5-27

Procedural types . . . . . . . . . . . . . . . . . . 5-28

Procedural types in statements

and expressions . . . . . . . . . . . . . . . . 5-29

Variant types . . . . . . . . . . . . . . . . . . . . 5-30

Variant type conversions . . . . . . . . . . . 5-31

Variants in expressions . . . . . . . . . . . . 5-33

Variant arrays . . . . . . . . . . . . . . . . . . 5-33

OleVariant . . . . . . . . . . . . . . . . . . . . 5-34

Type compatibility and identity . . . . . . . . . 5-34

Type identity . . . . . . . . . . . . . . . . . . 5-34

Type compatibility . . . . . . . . . . . . . . . 5-35

Assignment-compatibility . . . . . . . . . . . 5-35

Declaring types. . . . . . . . . . . . . . . . . . . 5-36

Variables . . . . . . . . . . . . . . . . . . . . . . 5-37

Declaring variables . . . . . . . . . . . . . . 5-37

Absolute addresses . . . . . . . . . . . . 5-38

Dynamic variables . . . . . . . . . . . . . 5-38

Thread-local variables . . . . . . . . . . . 5-38

Declared constants . . . . . . . . . . . . . . . . 5-39

True constants . . . . . . . . . . . . . . . . . 5-39

Constant expressions . . . . . . . . . . . 5-41

Resource strings . . . . . . . . . . . . . . 5-41

Typed constants . . . . . . . . . . . . . . . . 5-42

Array constants . . . . . . . . . . . . . . 5-43

Record constants . . . . . . . . . . . . . . 5-43

Procedural constants . . . . . . . . . . . 5-44

Pointer constants. . . . . . . . . . . . . . 5-44

Chapter 6

Procedures and functions 6-1

Declaring procedures and functions . . . . . . . 6-1

Procedure declarations . . . . . . . . . . . . . 6-2

Function declarations . . . . . . . . . . . . . . 6-3

Calling conventions . . . . . . . . . . . . . . . 6-4

Forward and interface declarations . . . . . . 6-5

External declarations . . . . . . . . . . . . . . 6-6

Linking to object files . . . . . . . . . . . . 6-6

Importing functions from libraries. . . . . 6-7

Overloading procedures and functions . . . . 6-8

Local declarations . . . . . . . . . . . . . . . 6-10

Nested routines . . . . . . . . . . . . . . 6-10

Parameters . . . . . . . . . . . . . . . . . . . . . 6-11

Parameter semantics . . . . . . . . . . . . . 6-11

Value and variable parameters . . . . . . 6-12

Constant parameters . . . . . . . . . . . 6-13

Out parameters. . . . . . . . . . . . . . . 6-13

Untyped parameters. . . . . . . . . . . . 6-14

String parameters . . . . . . . . . . . . . . . 6-15

Array parameters . . . . . . . . . . . . . . . 6-15

Open array parameters . . . . . . . . . . 6-15

Variant open array parameters . . . . . . 6-16

Default parameters . . . . . . . . . . . . . . 6-17

Default parameters and

overloaded routines . . . . . . . . . . . 6-18

Default parameters in forward and

interface declarations . . . . . . . . . . 6-19

Calling procedures and functions . . . . . . . . 6-19

Open array constructors . . . . . . . . . . . 6-19

Chapter 7

Classes and objects 7-1

Class types . . . . . . . . . . . . . . . . . . . . . . 7-2

Inheritance and scope . . . . . . . . . . . . . . 7-3

TObject and TClass . . . . . . . . . . . . . 7-3

Compatibility of class types . . . . . . . . 7-3

Object types . . . . . . . . . . . . . . . . . 7-4

Visibility of class members . . . . . . . . . . 7-4

Private, protected, and public members . 7-5

Published members. . . . . . . . . . . . . 7-5

Automated members . . . . . . . . . . . . 7-6

Forward declarations and mutually

dependent classes. . . . . . . . . . . . . . . 7-6

Fields . . . . . . . . . . . . . . . . . . . . . . . . 7-7

Methods. . . . . . . . . . . . . . . . . . . . . . . 7-8

Method declarations and implementations . 7-8

Inherited . . . . . . . . . . . . . . . . . . . 7-9

Self . . . . . . . . . . . . . . . . . . . . . . 7-9

Method binding . . . . . . . . . . . . . . . . 7-10

Static methods. . . . . . . . . . . . . . . . 7-10

Virtual and dynamic methods. . . . . . . 7-10

Abstract methods . . . . . . . . . . . . . . 7-12

Overloading methods . . . . . . . . . . . . . 7-12

Constructors . . . . . . . . . . . . . . . . . . 7-13

Destructors . . . . . . . . . . . . . . . . . . . 7-14

Message methods . . . . . . . . . . . . . . . 7-15

Implementing message methods . . . . . 7-16

Message dispatching . . . . . . . . . . . . 7-16

Properties . . . . . . . . . . . . . . . . . . . . . . 7-17

Property access . . . . . . . . . . . . . . . . . 7-17

Array properties . . . . . . . . . . . . . . . . 7-19

Index specifiers . . . . . . . . . . . . . . . . . 7-20

Storage specifiers . . . . . . . . . . . . . . . . 7-21

Property overrides and redeclarations . . . . 7-22

Class references . . . . . . . . . . . . . . . . . . 7-23

Class-reference types. . . . . . . . . . . . . . 7-23

Constructors and class references . . . . . 7-24

Class operators . . . . . . . . . . . . . . . . . 7-24

The is operator . . . . . . . . . . . . . . . 7-24

The as operator . . . . . . . . . . . . . . . 7-25

Class methods . . . . . . . . . . . . . . . . . 7-25

Exceptions . . . . . . . . . . . . . . . . . . . . . 7-26

When to use exceptions . . . . . . . . . . . . 7-26

Declaring exception types . . . . . . . . . . . 7-27

Raising and handling exceptions . . . . . . . 7-27

Try...except statements . . . . . . . . . . . 7-28

Re-raising exceptions . . . . . . . . . . . . 7-30

Nested exceptions . . . . . . . . . . . . . 7-31

Try...finally statements . . . . . . . . . . . 7-31

Standard exception classes and routines. . . 7-32

Chapter 8

Standard routines and I/O 8-1

File input and output . . . . . . . . . . . . . . . . 8-1

Text files . . . . . . . . . . . . . . . . . . . . . 8-3

Untyped files. . . . . . . . . . . . . . . . . . . 8-4

Text-file device drivers . . . . . . . . . . . . . . . 8-4

Device functions . . . . . . . . . . . . . . . . . 8-5

The Open function . . . . . . . . . . . . . . 8-5

The InOut function . . . . . . . . . . . . . 8-5

The Flush function . . . . . . . . . . . . . . 8-6

The Close function . . . . . . . . . . . . . . 8-6

Handling null-terminated strings . . . . . . . . . 8-6

Wide-character strings . . . . . . . . . . . . . 8-7

Other standard routines . . . . . . . . . . . . . . 8-7

Part II

Special topics

Chapter 9

Libraries and packages 9-1

Calling dynamically loadable libraries . . . . . . 9-1

Static loading . . . . . . . . . . . . . . . . . 9-1

Dynamic loading. . . . . . . . . . . . . . . 9-2

Writing dynamically loadable libraries . . . . . . 9-3

The exports clause. . . . . . . . . . . . . . . . 9-5

Library initialization code . . . . . . . . . . . 9-5

Global variables in a library . . . . . . . . . . 9-6

Libraries and system variables. . . . . . . . . 9-6

Exceptions and runtime errors in libraries . . 9-7

Shared-memory manager (Windows only) . . 9-8

Packages . . . . . . . . . . . . . . . . . . . . . . . 9-8

Package declarations and source files . . . . . 9-9

Naming packages . . . . . . . . . . . . . 9-10

The requires clause . . . . . . . . . . . . 9-10

The contains clause . . . . . . . . . . . . 9-10

Compiling packages . . . . . . . . . . . . . 9-11

Generated files . . . . . . . . . . . . . . . 9-11

Package-specific compiler directives . . 9-11

Package-specific command-line

compiler switches . . . . . . . . . . . . 9-12

Chapter 10

Object interfaces 10-1

Interface types . . . . . . . . . . . . . . . . . . . 10-1

IInterface and inheritance . . . . . . . . . . 10-2

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