Fortran 90 handbook : complete ANSI/ISO reference

835 Pages·2005·1.62 MB·English

by  Jeanne C Adams

Fortran 90 Handbook
Complete ANSI / ISO Reference
Jeanne C. Adams
Walter S. Brainerd
Jeanne T. Martin
Brian T. Smith
Jerrold L. Wagener
Intertext Publications
McGraw-Hill Book Company
Library of Congress Catalog Card Number 91-77211
Copyright © 1992 by Jeanne C. Adams, Walter S. Brainerd, Jeanne T. Martin, Brian T. Smith, and Jerrold L. Wagener. All rights
reserved. Printed in the United States of America. Except as permitted under the United States Copyright Act of 1976, no part of
this book may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system without the
prior written permission of the authors and the publisher.
10 9 8 7 6 5 4 3 2 1
ISBN 0-07-000406-4
Intertext Publications/Multiscience Press, Inc. One Lincoln Plaza New York, NY 10023
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Composition by UNICOMP
Preface
The Fortran90 Handbook is a definitive and comprehensive guide to Fortran90
and its use. Fortran90, the latest standard version of Fortran, has many
excellent new features that will assist the programmer in writing efficient,
portable, and maintainable programs. The Fortran 90 Handbook is an informal
description of Fortran 90, developed to provide not only a readable
explanation of features, but also some rationale for the inclusion of features
and their use. In addition, “models” give the reader better insight as to why
things are done as they are in the language.
This handbook is intended for anyone who wants a comprehensive survey of
Fortran90, including those familiar with programming language concepts but
unfamiliar with Fortran. Experienced Fortran77 programmers will be able to
use this volume to assimilate quickly those features in Fortran90 that are not
in Fortran77 (Fortran90 is a superset of Fortran77).
Chapter 0 provides a brief overview of several of the most important features
that are new in Fortran90. Chapters 1–14 correspond to Sections 1–14 in the
standard. (The standard is the complete official description of the language,
but it is written in a legally airtight, formal style without tutorial material and
can be difficult to understand in places.) The handbook and the standard can
be examined in parallel for insights into the Fortran language. This makes it
feasible to use this handbook to “decipher” the standard, and this is an ideal
use of this book.
Although the handbook is written for use in conjunction with the standard, it
is also designed as a practical stand-alone description of Fortran90. In the
interest of readability, a few of the more obscure aspects of the standard may
iii
not be treated rigorously; any such cases should not impact the usefulness of
this handbook in describing Fortran90. On the other hand, in places where the
standard is not completely clear, a reasonable interpretation is often given,
together with ways to implement and program that will avoid potential
problems due to misinterpretation of the standard. Of course, if information is
being sought to understand a fine point of compiler implementation, settle a
bet, resolve a court case, or determine the answer to a Fortran trivia question,
the standard itself should be considered the final authority.
The syntactic features of the language are described completely in the
appendices, and these can serve as continual concise references for Fortran90.
Other Sources of Information
Other parts of the book can be used to help find information.
•
Each of the intrinsic functions is described in detail in AppendixA,
although a general discussion of the intrinsic functions is included in
Chapter13.
•
The complete syntax of Fortran90 may be found in AppendixB. The syntax
rules are numbered exactly as they are in the Fortran standard. There is a
cross reference that lists, for each nonterminal syntactic term, the number of
the rule in which it is defined, and all rules in which it is referenced.
•
Appendix C contains a listing of the obsolescent features.
•
The index is unusually comprehensive.
•
There is an index of examples, giving the location of program examples that
illustrate the use of many Fortran90 features.
For an informal and tutorial approach to learning Fortran90, the book,
Programmers Guide to Fortran 90, Second Edition, by Brainerd, Goldberg, and
Adams (Unicomp, Albuquerque, NM, 1993) is more appropriate.
Style of the Programming Examples
In order to illustrate many features of the language and as many uses of these
features as possible, no single particular style has been used when writing the
examples. In many cases, the style illustrated is not necessarily one that the
authors recommend.
iv FORTRAN User’s Guide
Acknowledgments
Material in the appendices of this book was developed by the ANSI committee
X3J3 and the ISO committee SC22/WG5 for inclusion in the Fortran 90
standard ISO/IEC 1539 :1991. This material is reprinted with the permission of
the International Standards Organization.
Comments provided by Charles Goldberg have increased the accuracy and
readability of this book enormously.
Copyright
Fortran 90 Handbook is reproduced herein with the permission of McGraw-
Hill, Inc., Copyright 1992, by Walter S. Brainerd, Jeanne C. Adams, Jeanne T.
Martin, Brian T. Smith, and Jerrold L. Wagener. All rights reserved.
Printed Copies
Printed copies of this book may be obtained by ordering from
Unicomp, Inc.
1874 San Bernardino Ave NE
Albuquerque, NM 87122 USA
[phone]
[phone] (fax)
Visit the Fortran market: http://www.fortran.com/fortran
The home page includes how to order this book in hard copy.
Jeanne C. Adams
Walter S. Brainerd, [email protected]
Jeanne. T. Martin
Brian T. Smith
Jerrold L. Wagener
January 1992
v
vi FORTRAN User’s Guide
Table of Contents
Preface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
Sneak Preview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
1.1 History. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
1.2 Why a New Standard?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
1.3 Why Not Use Another Language?. . . . . . . . . . . . . . . . . . . 17
1.4 Development of Fortran 90 . . . . . . . . . . . . . . . . . . . . . . . . . 18
1.5 Fortran 77 Compatibility. . . . . . . . . . . . . . . . . . . . . . . . . . . 19
1.6 Extensibility. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
1.7 Intrinsic and Standard Modules. . . . . . . . . . . . . . . . . . . . . 20
1.8 The Fortran 90 Language Standard . . . . . . . . . . . . . . . . . . 21
1.9 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2. Fortran Concepts and Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2.1 Scope and Association. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2.2 Program Organization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.3 Data Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
2.4 Program Execution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
2.5 Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
2.6 Summary of Forms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
2.7 Ordering Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
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Copyright © 1992 J. Adams, W. Brainerd, J. Martin, B. Smith, and J. Wagener
2.8 Example Fortran 90 Program . . . . . . . . . . . . . . . . . . . . . . . 59
2.9 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
3. Language Elements
and Source Form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
3.1 The Processor Character Set . . . . . . . . . . . . . . . . . . . . . . . . 66
3.2 Lexical Tokens. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
3.3 Source Form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
3.4 Rules for Fixed/Free Source Form. . . . . . . . . . . . . . . . . . . 82
3.5 The INCLUDE Line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
3.6 Low-Level Syntax. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
3.7 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
4. Data Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
4.1 Building the Data Environment for a Problem Solution . 91
4.2 What Is Meant by “Type” in Fortran? . . . . . . . . . . . . . . . . 96
4.3 Intrinsic Data Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
4.4 Derived Types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
4.5 Structure Constructors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
4.6 Array Constructors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
4.7 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
5. Declarations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
5.1 Type Declaration Statements. . . . . . . . . . . . . . . . . . . . . . . . 134
5.2 Implicit Typing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
5.3 Array Properties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
5.4 Pointer Properties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
5.5 Value Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
5.6 Object Accessibility and Use. . . . . . . . . . . . . . . . . . . . . . . . 161
5.7 Procedure Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
5.8 Automatic Data Objects. . . . . . . . . . . . . . . . . . . . . . . . . . . . 174
5.9 NAMELIST Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
5.10 Storage Association . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
5.11 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
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6. Using Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
6.1 Constants and Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
6.2 Substrings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
6.3 Structure Components. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
6.4 Arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205
6.5 Pointers and Allocatable Arrays. . . . . . . . . . . . . . . . . . . . . 215
6.6 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222
7. Expressions and Assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . 227
7.1 Introduction to Fortran 90 Expressions. . . . . . . . . . . . . . . 228
7.2 Formation of Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . 234
7.3 Interpretation of Expressions . . . . . . . . . . . . . . . . . . . . . . . 276
7.4 Evaluation of Expressions. . . . . . . . . . . . . . . . . . . . . . . . . . 284
7.5 Assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290
7.6 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303
8. Controlling Execution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309
8.1 The Execution Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . 310
8.2 Blocks and Executable Constructs . . . . . . . . . . . . . . . . . . . 310
8.3 IF Construct and IF Statement . . . . . . . . . . . . . . . . . . . . . . 312
8.4 The CASE Construct. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 316
8.5 The DO Construct. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321
8.6 Branching. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333
8.7 Obsolescent Control Statements. . . . . . . . . . . . . . . . . . . . . 337
8.8 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341
9. Input and Output Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . 345
9.1 Records, Files, Access Methods, and Units. . . . . . . . . . . . 346
9.2 Data Transfer Statements. . . . . . . . . . . . . . . . . . . . . . . . . . . 359
9.3 Execution Model for Data Transfer Statements . . . . . . . . 389
9.4 Error and Other Conditions in Input/Output Statements 392
9.5 The OPEN Statement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395
9.6 The CLOSE Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 405
9.7 Inquiring about Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 408
9.8 File Positioning Statements. . . . . . . . . . . . . . . . . . . . . . . . . 417
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Copyright © 1992 J. Adams, W. Brainerd, J. Martin, B. Smith, and J. Wagener
9.9 Restrictions: I/O Specifiers, List Items, and Statements . 422
9.10 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 423
10. Input and Output Editing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427
10.1 Explicit Formatting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 429
10.2 Format Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 432
10.3 Character String Edit Descriptor Form . . . . . . . . . . . . . . . 435
10.4 Formatted Data Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . 436
10.5 File Positioning by Format Control . . . . . . . . . . . . . . . . . . 441
10.6 Numeric Editing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 442
10.7 Logical Editing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 455
10.8 Character Editing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 456
10.9 Control Edit Descriptors . . . . . . . . . . . . . . . . . . . . . . . . . . . 457
10.10 List-Directed Formatting. . . . . . . . . . . . . . . . . . . . . . . . . . . 465
10.11 Namelist Formatting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 471
10.12 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 480
11. Program Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 483
11.1 Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 483
11.2 Main Program. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 485
11.3 Internal Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 489
11.4 Host Association. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 491
11.5 External Subprograms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 496
11.6 Modules. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 498
11.7 Block Data Program Units. . . . . . . . . . . . . . . . . . . . . . . . . . 515
11.8 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 516
12. Using Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 521
12.1 Procedure Terms and Concepts . . . . . . . . . . . . . . . . . . . . . 522
12.2 Subroutines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 530
12.3 Functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 535
12.4 Procedure-Related Statements . . . . . . . . . . . . . . . . . . . . . . 543
12.5 Argument Association. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 548
12.6 Procedure Interfaces. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 573
12.7 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 587
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Copyright © 1992 J. Adams, W. Brainerd, J. Martin, B. Smith, and J. Wagener