This book is the second volume in a series entitled The Modula-2 Software Component Library. Charles Lins' collection of reusable standard software components could be the basis for every programmer's software project in Modula-2. Components that are implementations of commonly used data structures are presented, along with a description of their functionality and efficiency. Moreover, the books provide the background necessary to tailor these components to the specific needs of any Modula-2 environment. For every Modula-2 programmer, this series of books could prove as useful and indispensable as the original language reference by Niklaus Wirth. This second volume introduces software modules for lists, queues, and deques.

This book is the first volume in a series entitled The Modula-2 Software Component Library. Charles Lins collection of reusable standard software components, could be the basis for every programmers software project in Modula-2. Components that are implementations of commonly used data structures are presented, along with an adequate description of their functionality and efficiency. Moreover, the books provide the background necessary to tailor these components to the specific needs of any Modula-2 environment. For every Modula-2 programmer this series of books might prove as useful and indispensible as the original language reference by Niklaus Wirth.

Source Code Availability All of the source code found in this volume, and some that is not, is available from the author at a nominal fee. The author is interested in learning of any errors that may be found, though care has been taken in the construction of the modules to minimize these. The author is also interested in other comments, suggestions, recommendations, questions or experiences with the use of these modules. Contact the author through the following address: Modula-2 Software c/o Springer-Verlag 815 De La Vina St. Santa Barbara, CA 93101 As of February 1988, source code is available on 3.5" Macintosh diskettes (800K HFS format) for the TML Modula-2 compiler for MPW and the Mac METH Modula-2 compiler from ETH Ziirich. 1 Specification Requirements for specification of procedure and data abstractions were previously covered in Volume 1, Chapter 2. A summary is provided of the specification for mat used in this book. The format is adapted from that Guttag and Liskov 10] developed for the CLU language. It consists of relatively few constructs, is semi formal by providing a rigorous definition of the syntax and semantics of opera tions, and it provides powerful facilities for defining abstract data types. 1.1 Specification of Procedure Abstractions Specification of a procedure requires a full description of syntax and semantics. Syntax the name of the procedure by name, the name and type of each ar gument or result, and the order in which the arguments and results occur."

2 Source Code Availability All of the source code in this volume, and some that is not, is available from the author for $20. The author is also interested in learning of any errors that may be found, though care has been taken in the construction of the modules to minimize the possibility of their occurence. Any other comments, suggestions, recommenda- tions, questions, or experiences with the use of these modules would also be of interest. The reader may contact the author via the publisher at the following address: C. Lins: Modula-2 Source Code c/o Springer-Verlag 815 De La Vina Street Santa Barbara, CA 93101 USA As of February 1989, source code is available on two 3. 5" Macintosh diskettes (800K HFS format) for Bob Campbell's Modula-2 compiler for MPW(formerly TML Modula-2) and the MacMETH Modula-2 compiler from ETH Zurich. The author intends to port this software to both the SemperSoft and MetCom Modula- 2 compilers on the Macintosh. For the IBM PC (and compatibles) the software is available for TopSpeed Modula-2 (a product of JPI). The source code will soon be converted to work with Logitech's Modula-2 compiler as well as Stony Brook's Modula-2. Please mention your hardware platform as well as the volume(s) in which you are interested Development Environment The software for this volume was developed using the MPW (Macintosh(TM) Programmer' s Workshop) version 3. 0 and Bob Campbell's Modula-2 compiler ver- sion 1. 4d7.