scheme.texinfo

\input texinfo  @c -*-texinfo-*-

@settitle UMB Scheme Release Notes
@setfilename scheme.info

@ifinfo
This file documents the installation and use of UMB Scheme.

Copyright (C) 1988, 1996 William R Campbell.

Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
are preserved on all copies.

@ignore
Permission is granted to process this file through Tex and print the
results, provided the printed document carries copying permission
notice identical to this one except for the removal of this paragraph
(this paragraph not being relevant to the printed manual).

@end ignore
Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided also that the
section entitled ``GNU General Public License'' is included exactly as
in the original, and provided that the entire resulting derived work is
distributed under the terms of a permission notice identical to this one.

Permission is granted to copy and distribute translations of this manual
into another language, under the above conditions for modified versions,
except that the section entitled ``GNU General Public License'' and
this permission notice may be included in translations approved by the
Free Software Foundation instead of in the original English.
@end ifinfo

@setchapternewpage odd

@titlepage
@title @thistitle
@subtitle last updated Janaury 22, 1996
@subtitle $Revision: 3.2 $
@author William R Campbell
@page
@vskip 0pt plus 1filll
UMB Scheme Release Notes $Revision: 3.2 $
Copyright @copyright{} 1989, 1996 William R Campbell.

Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
are preserved on all copies.

Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided also that the
section entitled ``GNU General Public License'' is included exactly as
in the original, and provided that the entire resulting derived work is
distributed under the terms of a permission notice identical to this one.

Permission is granted to copy and distribute translations of this manual
into another language, under the above conditions for modified versions,
except that the section entitled ``GNU General Public License'' and
this permission notice may be included in translations approved by the
Free Software Foundation instead of in the original English.
@end titlepage
@page

@ifinfo
@node Top, Copying,, (DIR)
@ichapter Introduction

This manual documents how to install and use UMB Scheme as
well as its new features and incompatibilities, and how to report bugs.

@end ifinfo
@menu
* Copying::         GNU General Public License says
                     how you can copy and share GNU CC.
* Why::		    Why we implemented UMB Scheme.
* What::	    What's supported by UMB Scheme.
* Performance::	    Remarks on performance.
* Contributors::    People who have contributed to UMB Scheme.
* Installation::    How to compile and install UMB Scheme.
* Use::		    How to use UMB Scheme.
* Bugs::	    How to report bugs (if you want them fixed).
* Files::	    Distribution files.

@end menu

@node Copying, Why, Top, Top
@unnumbered GNU GENERAL PUBLIC LICENSE
@center Version 1, February 1989

@display
Copyright @copyright{} 1989 Free Software Foundation, Inc.
675 Mass Ave, Cambridge, MA 02139, USA

Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
@end display

@unnumberedsec Preamble

  The license agreements of most software companies try to keep users
at the mercy of those companies.  By contrast, our General Public
License is intended to guarantee your freedom to share and change free
software---to make sure the software is free for all its users.  The
General Public License applies to the Free Software Foundation's
software and to any other program whose authors commit to using it.
You can use it for your programs, too.

  When we speak of free software, we are referring to freedom, not
price.  Specifically, the General Public License is designed to make
sure that you have the freedom to give away or sell copies of free
software, that you receive source code or can get it if you want it,
that you can change the software or use pieces of it in new free
programs; and that you know you can do these things.

  To protect your rights, we need to make restrictions that forbid
anyone to deny you these rights or to ask you to surrender the rights.
These restrictions translate to certain responsibilities for you if you
distribute copies of the software, or if you modify it.

  For example, if you distribute copies of a such a program, whether
gratis or for a fee, you must give the recipients all the rights that
you have.  You must make sure that they, too, receive or can get the
source code.  And you must tell them their rights.

  We protect your rights with two steps: (1) copyright the software, and
(2) offer you this license which gives you legal permission to copy,
distribute and/or modify the software.

  Also, for each author's protection and ours, we want to make certain
that everyone understands that there is no warranty for this free
software.  If the software is modified by someone else and passed on, we
want its recipients to know that what they have is not the original, so
that any problems introduced by others will not reflect on the original
authors' reputations.

  The precise terms and conditions for copying, distribution and
modification follow.

@iftex
@unnumberedsec TERMS AND CONDITIONS
@end iftex
@ifinfo
@center TERMS AND CONDITIONS
@end ifinfo

@enumerate
@item
This License Agreement applies to any program or other work which
contains a notice placed by the copyright holder saying it may be
distributed under the terms of this General Public License.  The
``Program'', below, refers to any such program or work, and a ``work based
on the Program'' means either the Program or any work containing the
Program or a portion of it, either verbatim or with modifications.  Each
licensee is addressed as ``you''.

@item
You may copy and distribute verbatim copies of the Program's source
code as you receive it, in any medium, provided that you conspicuously and
appropriately publish on each copy an appropriate copyright notice and
disclaimer of warranty; keep intact all the notices that refer to this
General Public License and to the absence of any warranty; and give any
other recipients of the Program a copy of this General Public License
along with the Program.  You may charge a fee for the physical act of
transferring a copy.

@item
You may modify your copy or copies of the Program or any portion of
it, and copy and distribute such modifications under the terms of Paragraph
1 above, provided that you also do the following:

@itemize @bullet
@item
cause the modified files to carry prominent notices stating that
you changed the files and the date of any change; and

@item
cause the whole of any work that you distribute or publish, that
in whole or in part contains the Program or any part thereof, either
with or without modifications, to be licensed at no charge to all
third parties under the terms of this General Public License (except
that you may choose to grant warranty protection to some or all
third parties, at your option).

@item
If the modified program normally reads commands interactively when
run, you must cause it, when started running for such interactive use
in the simplest and most usual way, to print or display an
announcement including an appropriate copyright notice and a notice
that there is no warranty (or else, saying that you provide a
warranty) and that users may redistribute the program under these
conditions, and telling the user how to view a copy of this General
Public License.

@item
You may charge a fee for the physical act of transferring a
copy, and you may at your option offer warranty protection in
exchange for a fee.
@end itemize

Mere aggregation of another independent work with the Program (or its
derivative) on a volume of a storage or distribution medium does not bring
the other work under the scope of these terms.

@item
You may copy and distribute the Program (or a portion or derivative of
it, under Paragraph 2) in object code or executable form under the terms of
Paragraphs 1 and 2 above provided that you also do one of the following:

@itemize @bullet
@item
accompany it with the complete corresponding 
machine-readable
source code, which must be distributed under the terms of
Paragraphs 1 and 2 above; or,

@item
accompany it with a written offer, valid for at least three
years, to give any third party free (except for a nominal charge
for the cost of distribution) a complete machine-readable copy of the
corresponding source code, to be distributed under the terms of
Paragraphs 1 and 2 above; or,

@item
accompany it with the information you received as to where the
corresponding source code may be obtained.  (This alternative is
allowed only for noncommercial distribution and only if you
received the program in object code or executable form alone.)
@end itemize

Source code for a work means the preferred form of the work for making
modifications to it.  For an executable file, complete source code means
all the source code for all modules it contains; but, as a special
exception, it need not include source code for modules which are standard
libraries that accompany the operating system on which the executable
file runs, or for standard header files or definitions files that
accompany that operating system.

@item
You may not copy, modify, sublicense, distribute or transfer the
Program except as expressly provided under this General Public License.
Any attempt otherwise to copy, modify, sublicense, distribute or transfer
the Program is void, and will automatically terminate your rights to use
the Program under this License.  However, parties who have received
copies, or rights to use copies, from you under this General Public
License will not have their licenses terminated so long as such parties
remain in full compliance.

@item
By copying, distributing or modifying the Program (or any work based
on the Program) you indicate your acceptance of this license to do so,
and all its terms and conditions.

@item
Each time you redistribute the Program (or any work based on the
Program), the recipient automatically receives a license from the original
licensor to copy, distribute or modify the Program subject to these
terms and conditions.  You may not impose any further restrictions on the
recipients' exercise of the rights granted herein.

@item
The Free Software Foundation may publish revised and/or new versions
of the General Public License from time to time.  Such new versions will
be similar in spirit to the present version, but may differ in detail to
address new problems or concerns.

Each version is given a distinguishing version number.  If the Program
specifies a version number of the license which applies to it and ``any
later version'', you have the option of following the terms and conditions
either of that version or of any later version published by the Free
Software Foundation.  If the Program does not specify a version number of
the license, you may choose any version ever published by the Free Software
Foundation.

@item
If you wish to incorporate parts of the Program into other free
programs whose distribution conditions are different, write to the author
to ask for permission.  For software which is copyrighted by the Free
Software Foundation, write to the Free Software Foundation; we sometimes
make exceptions for this.  Our decision will be guided by the two goals
of preserving the free status of all derivatives of our free software and
of promoting the sharing and reuse of software generally.

@iftex
@heading NO WARRANTY
@end iftex
@ifinfo
@center NO WARRANTY
@end ifinfo

@item
BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW.  EXCEPT WHEN
OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
PROVIDE THE PROGRAM ``AS IS'' WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED
OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  THE ENTIRE RISK AS
TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU.  SHOULD THE
PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING,
REPAIR OR CORRECTION.

@item
IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL
ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
INCLUDING ANY GENERAL, SPECIAL, 
INCIDENTAL OR CONSEQUENTIAL DAMAGES
ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT
LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES
SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE
WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN
ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
@end enumerate

@iftex
@heading END OF TERMS AND CONDITIONS
@end iftex
@ifinfo
@center END OF TERMS AND CONDITIONS
@end ifinfo

@node Why, What, Copying, Top
@chapter Why We Implemented UMB Scheme

Our reasons form implementing yet another version of Scheme are the following:

@enumerate
@item
We use Scheme for modeling the operational semantics of programming languages
in our undergraduate languages course.  We wanted a Scheme system that was
easily ported to the various architectures on campus and that gave reasonable
run-time performance.

@item
We wanted to produce a relatively large piece if code as an example of good
program organization for our undergraduate and graduate software engineering
students.

@item
We wanted to involve students in all phases of the implementation effort,
including initial development, testing, extensions, and performance tuning.

@item
We wanted to illustrate that object-oriented design might successfully be
applied to programs written in vanilla programming languages such as C.

@end enumerate

Although this effort was meant as an exercise in design and programming, we
have ended up with what we think to be a rather nice interpreter.  It runs
relatively fast (performance comparisons with MIT Scheme are made below) and
we (as well as others not involved in development) have found the code 
very easy to maintain and extend.  

@node What, Performance, Why, Top 
@chapter What's Supported by UMB Scheme

UMB Scheme is an implementation of the language described in the 
@var{IEEE Standard for the Scheme Programming Language}
(December, 1990). It also supports R4RS (with the help of the Scheme Portable
Library (Aubrey Jaffrey) for high level macros.

All syntax, variables and procedures are implemented. 
Integers are implemented as fixnums and bignums, rationals as pairs of integers,
(inexact) reals as double-precision floats, and (inexact) complex numbers as 
pairs of double-precision floats.

For information on what additional functionality is supported, see the
man page (scheme.1).

The following files are loaded in order at startup:

If the variable SCHEME_INIT is set in the user's environment by executing
@example
        setenv SCHEME_INIT file
@end example
then file is loaded.

If SCHEME_INIT is not set and if a file 
@var{.scheme}
exists in the user's home directory then it is loaded.

The files named as optional arguments are loaded from left to right.

@node Performance, Contributors, What, Top
@chapter Remarks on Performance

So far as speed is concerned, UMB Scheme loses to MIT's C Scheme
in pure evaluation but performs significantly better than C Scheme when it
comes to compile-load-and-go.  

For example, consider the following @var{tak} benchmark code from
Richard P Gabriel, 
@var{Performance and Evaluation of Lisp Systems,}
MIT Press, 1985.
@example

; tak
; function-call-heavy; test of function call and recursion

(define (tak x y z)
  (if (not (< y x))
      z
      (tak (tak (- x 1) y z)
	   (tak (- y 1) z x)
	   (tak (- z 1) x y))))

(tak 18 12 6)

@end example
On a Sun 3/140, C Scheme gets through this in 75 seconds while UMB Scheme
takes 98 seconds; in this instance C Scheme runs faster.

But consider a definition-heavy file of code such as the following.
@example

(define (fac x) (if (= x 0) 1 (* x (fac (- x 1))) ))
(fac 5)

(define (fac x) (if (= x 0) 1 (* x (fac (- x 1))) ))
(fac 5)

(define (fac x) (if (= x 0) 1 (* x (fac (- x 1))) ))
(fac 5)

;; ...  1000 copies 

@end example
To get through these 1000 definitions of (and calls to) @var{fac},
C Scheme takes 432 seconds but UMB Scheme takes only 19 seconds;
in this instance UMB Scheme runs 22 times faster than C Scheme.

Therefore, UMB Scheme appears to do much better in a heavy compile-load-and-go
environment (such as one would find in an undergraduate languages course)
than in raw computation.  

Space is more difficult to address when comparing Scheme systems since it 
depends on one's choice for a heap size.  UMB Scheme's load module has a size
of 216K bytes; C Scheme's load module is 279K bytes.  As they are currently
configured, UMB Scheme runs in a 1600K region as compared to C Scheme's 3944K 
(as measured by top(1) on Unix).  
UMB Scheme's storage allocator begins with a small
(200K byte) heap and increases heap size as necessary (and as permitted by the
operating system) at garbage collection time.


@node Contributors, Installation, Performance, Top
@chapter Contributors to UMB Scheme

@itemize @bullet
@item
The interpreter is based on the Explicit-Control Evaluator described
in the textbook: Harold Abelson and Gerald Jay Sussman,
@var{Structure and Interpretation of Computer Programs},
MIT Press, Cambridge, Massachusetts, 1985.

@item
Bill Campbell was the primary author and project manager.

@item
The idea of organizing the control of the interpreter around objects
comes from Richard Schooler.

@item
Karl Berry and Kathy Hargreaves helped with the initial programming.

@item
Bill McCabe coded some performance improvements,
particularly lexical variable addressing.

@item
Mary Glaser, Tim Holt, Long Nguyen and Thang Quoc Tran worked on numbers.

@item
Ira Gerstein and Jeyashree Sivasubram help bring UMB Scheme up to R4RS
standard.

@item
Barbara Dixey, Susan Quina and Bela Sohoni coded some additional
performance improvements, handling varying numbers of arguments to
functions in C.

@item
John Tam rewrote the macro facility for supporting defmacro and for
interfacing to the Scheme Portable Library.
@item
Many undergraduate students at UMB wrote test programs and offered
suggestions for improvement.

@end itemize


@node Installation, Use, Contributors, Top
@chapter Compiling and Installing UMB Scheme

UMB Scheme has been installed successfully using both @var{cc} and @var{gcc}
(the Gnu C compiler) on the following machines and operating systems:

@itemize @bullet

@item
Sun 3 and Sun 4 running Unix.

@item
Sun 386i running Sun Unix 4.0.1.

@item
DEC Vax 11/750 running Unix 4.3 BSD.

@item DEC Decstation 5000 running Ultrix.
@end itemize

UMB Scheme was written so as to be easily ported to other systems. 
Some modifications may be required.

To install UMB Scheme one of the systems listed above, simply go into
the distribution directory and do the following.

@enumerate 

@item
Carefully read the file portable.h file.  Any minor modifications will
want to be made here.

Of particular importance are ALIGNMENT, NEGATIVE_ADDRESSES and the 
definition for Intergral_Pointer; see portable.h for details.

@item
Compile UMB Scheme using the @file{Makefile} provided.  If you have the Gnu
C Compiler, @var{gcc}, then simply type
@example

	make

@end example
or,
@example

	make CC=gcc

@end example

Otherwise, to use @var{cc}, type
@example

	make CC=cc CFLAGS=-O

@end example

This will compile all necessary source files and create the executable
file @file{scheme}.

@item
Install the executable file in some public bin, e.g.
@example

	cp scheme /usr/local/bin/scheme

@end example

@item
Install the UMB Scheme @var{standard prelude} in the public library.
@example

	mkdir /usr/local/lib/scheme
	cp prelude.scheme /usr/local/lib/scheme

@end example
This pathname is wired into UMB Scheme.  If necessary, you can change
the definition of @code{STANDARD_PRELUDE_FILENAME} 
in the source file @file{steering.c}.

@item
Install the SLIB directory.
@example

        cp -r slib /usr/local/lib  # not in /scheme
        cp SLIB-for-umb-scheme.init /usr/local/lib/scheme

@end example
The standard prelude, @code{prelude.scheme}, assumes that the start up file
@code{SLIB-for-umb_scheme.init} is here; if you put it somewhere else,
modify @code{prelude.scheme} accordingly.

If you do not wish to use SLIB, then comment out the load near the end 
of @code{prelude.scheme}.
@item
Copy the manual page to the appropriate directory, e.g.
@example
	cp scheme.l /usr/spool/man/man1
@end example
Some shops maintain a separate @file{manl} directory for local manual pages;
consult your local system administrator.
@end enumerate

That should do it!

@node Use, Bugs, Installation, Top
@chapter Using UMB Scheme

Invoking UMB Scheme is straightforward; simply type
@example
	scheme [names of any scheme files to be loaded]
@end example

To get out of UMB Scheme type @code{Control-D}.

See the man pages (scheme.l) for details.

@node Bugs, Files, Use, Top
@chapter What To Do About Bugs

UMB Scheme has been used by many undergraduate students and several bugs
have been exposed and repaired.  No doubt, bugs remain.  The author 
would appreciate hearing about any bugs found (and any fixes made).

Send reports to
@example
	bill@@cs.umb.edu
@end example
or, by postal service, to
@example
	Bill Campbell
	Department of Mathematics and Computer Science
	University of Massachusetts at Boston
	Harbor Campus
	Boston, MA 02125

	617-287-6449
@end example

@node Files, Top, Bugs, Top
@chapter Distribution files

@example
Distribution Files for UMB Scheme Version 1.1

README               This list of files.
scheme.texinfo       UMB Scheme Release Notes.
Makefile             For compiling UMB Scheme.
prelude.scheme       The Scheme prelude, primitives loaded at start.
scheme.l             UMB Scheme manual page (in man(1) format).


Source files:

portable.h           Portability considerations.

steering.c           UMB Scheme steering -- including main().
steering.h

debug.c              Debugger steering and debug primitives.
debug.h

architecture.c       Registers, stacks, heap, name handling.
architecture.h

object.c             Scheme objects.
object.h

io.c                 Read, display, print, file handling.
io.h

compiler.c           Compiler: Expression -> Graph.
compiler.h

eval.c               Eval().
eval.h

primitive.c          (Non-numeric) primitives implemented in C.
primitive.h

number.c             Number primitives.
number.h     

bignum.c             Bignum (integers of arbitrary magnitude).
bignum.h

complex.c            Complex number support.
complex.h

fixnum.c             Fixnum (smaller integers) support.
fixnum.h

real.c               Real number (C double) support.
real.h

rational.c           NB: rationals not yet implemented (skeletons).
rational.h

See the Release Notes (scheme.texinfo) for installation.
@end example
@contents
@bye