Scheme 9 from Empty Space
	A Portable Scheme Interpreter with a Unix Interface
	By Nils M Holm, 2007-2016

	S9fES is a mature, portable, and comprehensible public-domain
	interpreter for R4RS Scheme offering

	- bignum arithmetics
	- decimal-based real number arithmetics
	- support for low-level Unix programming
	- cursor addressing with Curses
	- basic networking procedures
	- loads of useful library functions

	It is written in ANSI C (C89) and Scheme and it runs in many
	popular environments, including *BSD, Linux, Plan 9, and the
	unmentionable horror (although the Plan 9 and Horror versions
	will exclude the Unix, Curses, and Networking extensions).

	The S9fES code strives to be simple and comprehensible. It is
	particularly interesting to people who want to

	- have a Scheme system that runs virtually everywhere
	- write Unix programs in a high-level language
	- try Scheme without having to jump through too many hoops
	- study the implementation of Scheme
	  (in a language other than Scheme)

	There is a book describing the S9 implementation in detail. It
	is available in print and PDF format. See

	S9fES supports the following SRFI's: 
	- SRFI-0:  feature-based conditional expansion (subset)
	- SRFI-2:  AND-LET*                            (subset)
	- SRFI-22: running Scheme scripts on Unix
	- SRFI-23: error reporting mechanism
	- SRFI-30: nested multi-line comments
	- SRFI-43: vector library                      (subset)


	You can run the interpreter in its build directory without
	installing it. Just type "cc -Dunix -o s9 s9.c" (or -Dplan9)
	and then "./s9".

	The S9 code is only loosely coupled to its Makefile, so in most
	cases running "cc -Dunix -o s9 s9.c" or "8c -Dplan9 -o s9 s9.c"
	will compile the interpreter just fine. (However, doing so will
	not include the Unix/Curses/Networking extensions.)

	On most systems of the Unix family (plus CygWin and MinGW),
	you can compile and install S9fES by running "make install".

	Once installed, typing "s9" will start the interpreter.

	,h  explains the online help system.
	,a  returns a list of all help topics (long!).

	If the above commands do not work, try  ,l contrib/help.scm



	To compile S9fES, run "make" and then "make test" (this will run
	the test suite to make sure that the interpreter works properly).
	Running "make tests" will run even more tests.

	On 64-bit systems, you may have to add the -DBITS_PER_WORD_64
	define to the Makefile. Not doing so will probably still work,
	but may result in slightly worse bignum performance.

	You can install S9fES (including the goodies) on a Unix system
	by typing "make install" as root, but before doing so, please
	edit at least the PREFIX variable at the beginning of Makefile.
	(Be sure to re-compile S9fES (make clean; make) after changing
	 PREFIX, because it is used to set up some internal paths).

	Plan 9

	Before installing, run "rc util/fix-help-files". The help/
	directory contains symlinks, and the above script replaces
	them by copies.

	To compile S9fES on Plan 9 from Bell Labs, just type "mk".
	The "test" and "tests" targets will run tests, just like on

	To install S9fES, run "mk inst". It will copy the S9fES binary,
	heap image, function library, and help files to $s9dir (which
	defaults to /lib/s9fes). Edit mkfile if you prefer a different

	The install procedure will also copy the file util/s9.rc to
	/rc/bin/s9 and adjust the $s9dir variable in that file.

	Manual Installation

	To install S9fES manually,

	- Compile s9 with a proper library path (the one hardwired in
	  "s9.h" is probably not what you want). E.g.:

	  cc -o s9 -DLIBRARY_PATH="\"your-path\"" s9.c

	  A reasonable value for "your-path" would be, for example:


	  Security-sensitive people may consider (re)moving the dot.

	- Copy the "s9" binary to a location where it can be executed
	  (e.g. /usr/local/bin).

	- Copy the file "s9.scm" to a publicly readable directory
	  (default: /usr/local/share/s9fes). This directory will be
	  referred to as S9DIR in the following instructions. Note
	  that this directory *must* be contained in LIBRARY_PATH,
	  as defined above.

	- Compile a heap image and copy it to S9DIR:

	  s9 -i - -d s9.image

	  The image file must have the same base name as the interpreter
	  or it will not be loaded. An image loads significantly faster
	  than source code.


	- Copy the content of the "lib" directory to S9DIR. This
	  directory contains lots of useful Scheme functions.

	- Copy the content of the "contrib" directory to S9DIR. These
	  files contain additional Scheme functions contributed by other
	  authors and/or imported from various sources.

	- Create a subdirectory named "help" in S9DIR and copy the
	  content of the "help" directory to S9DIR/help. These files
	  are part of the interactive help system.

	- Copy the nroff(1) source code of the manual page "s9.1" to
	  section 1 of your online manual (e.g. /usr/local/man/man1).
	  In case you are not running Unix, there is a pre-formatted
	  copy in the file "s9.1.txt".


	You may create the S9FES_LIBRARY_PATH environment variable and
	make it point to S9DIR as well as other directories that
	contain Scheme programs. The variable may contain a single
	directory or a colon-separated list of directories that will be
	searched in sequence for image files, library files, and help
	pages (in "help" subdirectories contained in the given paths).

	S9FES_LIBRARY_PATH overrides LIBRARY_PATH, so all directories
	listed in the latter should also be present in the former.

	To create an image file containing additional functionality,
	add the desired options to the "config.scm" file and run

	s9 -i - -l config.scm -d s9.image

	(This step is already included in the default Unix Makefile and
	 Plan 9 mkfile).


	Typing "s9" will drop you into the read-eval-print loop of the
	interpreter. You can run Scheme programs non-interactively by
	typing "s9 -f program.scm" (or just "s9 program.scm") at your
	shell prompt.

	If you installed the extension library functions in S9DIR,
	they can be loaded by the LOAD-FROM-LIBRARY procedure or the
	",l" (comma ell) meta command:

	> ,l draw-tree
	; loading from /usr/local/share/s9fes/draw-tree.scm
	> (draw-tree '(a b c))
	 |       |       |
	 a       b       c
	> _

	Feel free to explore them.

	Running "s9help topic" on the shell prompt will print the S9fES
	online help page about the given topic.


	If compiled in, there are some extension procedures providing
	access to some Unix system calls, some networking procedures,
	and a Curses interface. To compile these extensions, uncomment
	the corresponding EXTRA_ lines in the Makefile. (In fact, all
	extensions are compiled in by default on Unix.)


	I would like to thank the following people and organisations for
	patches, bug reports, suggestions, hardware, access to hardware,

	Alexander Shendi, Arun Srinivasan, Bakul Shah, Barak Pearlmutter,
	Blake McBride, Bsamograd (reddit), David Person, Dig1 (reddit),
	Dirk Lutzebaeck, Doug Currie, Mario Deilmann, Masaru KIMURA,
	Nullbuilt0 (reddit), Ray Lai, Torsten Leibold, Yi Dai,
	and the Super Dimension Fortress (SDF.ORG).


	Nils M Holm < n m h @ t 3 x . o r g >