____  ____  ____  ____  ____
	Scheme 9 from Empty Space      / ___)/ __ \|  __)|  __)/ ___)
	A Portable Scheme Interpreter  \___ \\__  /|  __)|  __)\___ \
	By Nils M Holm, 2007-2018      (____/(___/ |_|   |____)(____/

	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
	- an integrated online help system
	- loads of useful library functions

	It is written in ANSI C (C89) and Scheme and 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

	There is a book describing a previous S9 implementation
	in detail. It is available in print and PDF format. See
	http://t3x.org/s9book/

	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)

	Bakul Shah maintains a downstream repository with extended
	Plan 9 support, like access to system functions and an FFI:
	https://github.com/bakul/s9fes.  Please send any feedback
	regarding the Plan 9 extension directly to him.


	QUICK START

	You can run an S9 interpreter in its build directory without
	installing it. Just type

	    cc -o s9 s9.c s9core.c
	    ./s9 -i - -d s9.image

	and then "./s9". You might have to add -Dplan9 on Plan 9 systems.
	The interpreter will support full R4RS Scheme, but none of the
	extensions provided by S9 (Unix system calls, Curses, etc).

	A quick test of the interpreter can be performed by running

	    ./s9 util/test.scm

	In order to bring up the online help system, run

	    ./s9 -l contrib/help.scm -d s9.image

	When running ./s9 for the next time, the following help commands
	will be available:

	    ,h  explain the online help system
	    ,a  return a list of all help topics (long!)

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

	See below for further instructions.


	COMPILING AND INSTALLING

	Unix

	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.

	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

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

	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
	location.

	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 image directory and library path (the
	  ones hardwired in "s9.c" are probably not what you want). E.g.:

	  cc -o s9 -DIMAGE_DIR="\"dir\"" -DLIBRARY_PATH="\"path\"" \
		s9.c s9core.c

	  where "dir" should be set to S9DIR, as described below, and a
	  reasonable value for "path" would be

	  ".:~/s9fes:/usr/local/share/s9fes"

	  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).

	- Select a publicly readable directory to contain library files.
	  (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

	  This step requires the file "s9.scm" to be present in the
	  current directory.

	  The image file must be named "s9.image" or it will not be
	  loaded by default. An image loads significantly faster than
	  source code.

	Optionally:

	- 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. Note that help/
	  does contain subdirectories!

	- 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".


	CONFIGURATION

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

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

	and copy the resulting image to your IMAGE_DIR.

	If you are keeping your image files in a location other than
	S9DIR, you can create the S9FES_IMAGE_DIR environment variable
	and make it point to your preferred location. In this case
	"s9 -i foo.image" will load $S9FES_IMAGE_DIR/foo.image.

	You may also 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 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.


	GETTING STARTED

	Typing "s9" will drop you into the read-eval-print loop of the
	interpreter. You can run Scheme programs non-interactively by
	typing "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))
	[o|o]---[o|o]---[o|/]
	 |       |       |
	 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.


	ACKNOWLEDGEMENTS

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

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


	CONTACT

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