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      The programmers of old were mysterious and profound.  We
   cannot fathom their thoughts, so all we do is describe their
      Aware, like a fox crossing the water.  Alert, like a general
   on the battlefield.  Kind, like a hostess greeting her guests.
      Simple, like uncarved blocks of wood.  Opaque, like black 
   pools in darkened caves.
      Who can tell the secrets of their hearts and minds?
      The answer exists only in the Tao.
         -- Geoffrey James, "The Tao of Programming"


SBCL is derived from the 18b version of CMU CL.

Most of CMU CL was originally written as part of the CMU Common Lisp
project at Carnegie Mellon University. According to the documentation
in CMU CL 18b,
    Organizationally, CMU Common Lisp was a small, mostly autonomous
  part within the Mach operating system project. The CMU CL project
  was more of a tool development effort than a research project.
  The project started out as Spice Lisp, which provided a modern
  Lisp implementation for use in the CMU community.
  CMU CL has been under continuous development since the early 1980's
  (concurrent with the Common Lisp standardization effort.) 
Apparently most of the CMU Common Lisp implementors moved on to
work on the Gwydion environment for Dylan.

CMU CL's CLOS implementation is derived from the PCL reference
implementation written at Xerox PARC.

CMU CL's implementation of the LOOP macro was derived from code
from Symbolics, which was derived from code from MIT.

CMU CL had many individual author credits in the source files. In the
sometimes-extensive rearrangements which were required to make SBCL
bootstrap itself cleanly, it was tedious to try keep such credits
attached to individual source files, so they have been moved here

Bill Newman <> did this transformation, and
so any errors made are probably his. Corrections would be appreciated.


The original headers of the PCL files contained the following text:

;;; Any person obtaining a copy of this software is requested to send their
;;; name and post office or electronic mail address to:
;;;   CommonLoops Coordinator
;;;   Xerox PARC
;;;   3333 Coyote Hill Rd.
;;;   Palo Alto, CA 94304
;;; (or send Arpanet mail to
;;; Suggestions, comments and requests for improvements are also welcome.

This was intended for the original incarnation of the PCL code as a
portable reference implementation. Since our version of the code has
had its portability hacked out of it, it's no longer particularly
relevant to any coordinated PCL effort (which probably doesn't exist
any more anyway). Therefore, this contact information has been deleted
from the PCL file headers.

A few files in the original CMU CL 18b src/pcl/ directory did not
carry such Xerox copyright notices:
  * Some code was originally written by Douglas T. Crosher for CMU CL:
    ** the Gray streams implementation
    ** the implementation of DOCUMENTATION as methods of a generic
  * generic-functions.lisp seems to have been machine-generated.

The comments in the CMU CL 18b version of the PCL code walker,
src/pcl/walk.lisp, said in part
;;;   a simple code walker, based IN PART on: (roll the credits)
;;;      Larry Masinter's Masterscope
;;;      Moon's Common Lisp code walker
;;;      Gary Drescher's code walker
;;;      Larry Masinter's simple code walker
;;;      .
;;;      .
;;;      boy, thats fair (I hope).


The src/code/loop.lisp file from CMU CL 18b had the following
credits-related information in it:

;;;   The LOOP iteration macro is one of a number of pieces of code
;;;   originally developed at MIT for which free distribution has been
;;;   permitted, as long as the code is not sold for profit, and as long
;;;   as notification of MIT's interest in the code is preserved.
;;;   This version of LOOP, which is almost entirely rewritten both as
;;;   clean-up and to conform with the ANSI Lisp LOOP standard, started
;;;   life as MIT LOOP version 829 (which was a part of NIL, possibly
;;;   never released).
;;;   A "light revision" was performed by me (Glenn Burke) while at
;;;   Palladian Software in April 1986, to make the code run in Common
;;;   Lisp. This revision was informally distributed to a number of
;;;   people, and was sort of the "MIT" version of LOOP for running in
;;;   Common Lisp.
;;;   A later more drastic revision was performed at Palladian perhaps a
;;;   year later. This version was more thoroughly Common Lisp in style,
;;;   with a few miscellaneous internal improvements and extensions. I
;;;   have lost track of this source, apparently never having moved it to
;;;   the MIT distribution point. I do not remember if it was ever
;;;   distributed.
;;;   The revision for the ANSI standard is based on the code of my April
;;;   1986 version, with almost everything redesigned and/or rewritten.

The date of the M.I.T. copyright statement falls around the time
described in these comments. The dates on the Symbolics copyright
statement are all later -- the earliest is 1989.


CMU CL's symbol (but not package) code (code/symbol.lisp) was
originally written by Scott Fahlman and updated and maintained
by Skef Wholey.

The CMU CL reader (code/reader.lisp) was originally the Spice Lisp
reader, written by David Dill and with support for packages added by
Lee Schumacher. David Dill also wrote the sharpmacro support

CMU CL's package code was rewritten by Rob MacLachlan based on an
earlier version by Lee Schumacher. It also includes DEFPACKAGE by Dan
Zigmond, and WITH-PACKAGE-ITERATOR written by Blaine Burks. William
Lott also rewrote the DEFPACKAGE and DO-FOO-SYMBOLS stuff.

CMU CL's string code (code/string.lisp) was originally written by
David Dill, then rewritten by Skef Wholey, Bill Chiles, and Rob

Various code in the system originated with "Spice Lisp", which was
apparently a predecessor to the CMU CL project. Much of that was
originally written by Skef Wholey:
	code/seq.lisp, generic sequence functions, and COERCE
	code/array.lisp, general array stuff
	code/list.lisp, list functions (based on code from Joe Ginder and
		Carl Ebeling)
The CMU CL seq.lisp code also gave credits for later work by Jim Muller
and Bill Chiles.

The modules system (code/module.lisp, containing REQUIRE, PROVIDE,
and friends, now deprecated by ANSI) was written by Jim Muller and 
rewritten by Bill Chiles.

The CMU CL garbage collector was credited to "Christopher Hoover,
Rob MacLachlan, Dave McDonald, et al." in the CMU CL code/gc.lisp file,
with some extra code for the MIPS port credited to Christopher Hoover
alone. The credits on the original "gc.c", "Stop and Copy GC based
on Cheney's algorithm", said "written by Christopher Hoover".

Guy Steele wrote the original character functions
They were subsequently rewritten by David Dill, speeded up by Scott
Fahlman, and rewritten without fonts and with a new type system by Rob

Lee Schumacher made the Spice Lisp version of backquote. The comment
in the CMU CL sources suggests he based it on someone else's code for
some other Lisp system, but doesn't say which. A note in the CMU CL
code to pretty-print backquote expressions says that unparsing support
was provided by Miles Bader.

The CMU implementations of the Common Lisp query functions Y-OR-N-P
and YES-OR-NO-P were originally written by Walter van Roggen, and 
updated and modified by Rob MacLachlan and Bill Chiles.

The CMU CL sort functions (code/sort.lisp) were written by Jim Large,
hacked on and maintained by Skef Wholey, and rewritten by Bill Chiles.

Most of the internals of the Python compiler seem to have been
originally written by Robert MacLachlan:
	the type system and associated "cold load hack magic"
	the lexical environment database
		compiler/globaldb.lisp, etc.
	the IR1 representation and optimizer
		compiler/ir1*.lisp, etc.
	the IR2 representation and optimizer
		compiler/ir2*.lisp, etc.
	many concrete optimizations
		compiler/srctran.lisp (with some code adapted from
			CLC by Wholey and Fahlman)
		compiler/float-tran.lisp, etc.
	information about optimization of known functions
	debug information representation
		compiler/debug.lisp, compiler/debug-dump.lisp
	memory pools to reduce consing by reusing compiler objects
	toplevel interface functions and drivers
Besides writing the compiler, and various other work mentioned elsewhere,
Robert MacLachlan was also credited with tuning the implementation of 
streams for Unix files, and writing
	various floating point support code
		code/float-trap.lisp, floating point traps
		code/float.lisp, misc. support a la INTEGER-DECODE-FLOAT
	low-level time functions

William Lott is also credited with writing or heavily maintaining some
parts of the CMU CL compiler. He was responsible for lifting 
compiler/meta-vmdef.lisp out of compiler/vmdef.lisp, and also wrote
	various optimizations
		compiler/seqtran.lisp (with some code adapted from an older
			seqtran written by Wholey and Fahlman)
	the separable compiler backend
	the implementation of LOAD-TIME-VALUE
	the most recent version of the assembler
	vop statistics gathering
	centralized information about machine-dependent and..
	..machine-independent FOO, with
		compiler/generic/vm-fndb.lisp, FOO=function signatures
		compiler/generic/vm-typetran.lisp, FOO=type ops
		compiler/generic/objdef.lisp, FOO=object representation
		compiler/generic/primtype.lisp, FOO=primitive types
Also, Christopher Hoover and William Lott wrote compiler/generic/vm-macs.lisp 
to centralize information about machine-dependent macros and constants.

Sean Hallgren is credited with most of the Alpha backend.  Julian
Dolby created the CMU CL Alpha/Linux port. Douglas Crosher added
complex-float support.

The original PPC backend was the work of Gary Byers.  Some bug fixes
and other changes to update it for current CMUCL interfaces were made 
by Eric Marsden and Douglas Crosher

The CMU CL machine-independent disassembler (compiler/disassem.lisp)
was written by Miles Bader.

Parts of the CMU CL system were credited to Skef Wholey and Rob
MacLachlan jointly, perhaps because they were originally part of Spice
Lisp and were then heavily modified:
	code/load.lisp, the loader, including all the FASL stuff
	code/macros.lisp, various fundamental macros
	code/mipsstrops.lisp, primitives for hacking strings
	code/purify.lisp, implementation of PURIFY
	code/stream.lisp, stream functions
	code/lispinit.lisp, cold startup
	code/profile.lisp, the profiler

Bill Chiles also modified code/macros.lisp. Much of the implementation
of PURIFY was rewritten in C by William Lott.

The CMU CL number functions (code/number.lisp) were written by Rob
MacLachlan, but acknowledge much code "derived from code written by 
William Lott, Dave Mcdonald, Jim Large, Scott Fahlman, etc."

CMU CL's weak pointer support (code/weak.lisp) was written by
Christopher Hoover.

The CMU CL DEFSTRUCT system was credited to Rob MacLachlan, William
Lott and Skef Wholey jointly.

The FDEFINITION system for handling arbitrary function names (a la
(SETF FOO)) was originally written by Rob MacLachlan. It was modified
by Bill Chiles to add encapsulation, and modified more by William Lott
to add FDEFN objects.

The CMU CL condition system (code/error.lisp) was based on
some prototyping code written by Ken Pitman at Symbolics.

The CMU CL HASH-TABLE system was originally written by Skef Wholey
for Spice Lisp, then rewritten by William Lott, then rewritten
again by Douglas T. Crosher.

The support code for environment queries (a la LONG-SITE-NAME),
the DOCUMENTATION function, and the DRIBBLE function was written
and maintained "mostly by Skef Wholey and Rob MacLachlan. Scott
Fahlman, Dan Aronson, and Steve Handerson did stuff here too."
The same credit statement was given for the original Mach OS interface code.

The CMU CL printer, print.lisp, was credited as "written by Neal
Feinberg, Bill Maddox, Steven Handerson, and Skef Wholey, and modified
by various CMU Common Lisp maintainers." The comments on the float
printer said specifically that it was written by Bill Maddox. The
comments on bignum printing said specifically that it was written by
Steven Handerson (based on Skef's idea), and that it was rewritten by
William Lott to remove assumptions about length of fixnums on the MIPS

The comments in the main body of the CMU CL debugger 
say that it was written by Bill Chiles. Some other related files
	code/debug-int.lisp, programmer's interface to the debugger
	code/ntrace.lisp, tracing facility based on breakpoints
say they were written by Bill Chiles and Rob MacLachlan.
The related file
	src/debug-vm.lisp, low-level support for :FUNCTION-END breakpoints
was written by William Lott.

The CMU CL GENESIS cold load system,
compiler/generic/new-genesis.lisp, was originally written by Skef
Wholey, then jazzed up for packages by Rob MacLachlan, then completely
rewritten by William Lott for the MIPS port.

The CMU CL IR1 interpreter was written by Bill Chiles and Robert

Various CMU CL support code was written by William Lott:
	the bytecode interpreter
	bitblt-ish operations a la SYSTEM-AREA-COPY
	Unix interface
		code/fd-stream.lisp, Unix file descriptors as Lisp streams
		code/filesys.lisp, other Unix filesystem interface stuff
	handling errors signalled from assembly code
	finalization based on weak pointers
	irrational numeric functions
	the pretty printer
	predicates (both type predicates and EQUAL and friends)
	saving the current Lisp image as a core file
	handling Unix signals
	implementing FORMAT

The ALIEN facility seems to have been written largely by Rob
MacLachlan and William Lott. The CMU CL comments say "rewritten again,
this time by William Lott and Rob MacLachlan," but don't identify who
else might have been involved in earlier versions.

The comments in CMU CL's code/final.lisp say "the idea really was
Chris Hoover's". The comments in CMU CL's code/pprint.lisp say "Algorithm
stolen from Richard Waters' XP." The comments in CMU CL's code/format.lisp
say "with lots of stuff stolen from the previous version by David Adam
and later rewritten by Bill Maddox."

Jim Muller was credited with fixing seq.lisp.

CMU CL's time printing logic, in code/format-time.lisp, was written
by Jim Healy.

Bill Chiles was credited with fixing/updating seq.lisp after Jim Muller.

The CMU CL machine/filesystem-independent pathname functions
(code/pathname.lisp) were written by William Lott, Paul Gleichauf, and
Rob MacLachlan, based on an earlier version written by Jim Large and
Rob MacLachlan.

Besides writing the original versions of the things credited to him
above, William Lott rewrote, updated, and cleaned up various stuff:

The INSPECT function was originally written by Blaine Burks.

The CMU CL DESCRIBE facility was originally written by "Skef Wholey or
Rob MacLachlan", according to the comments in the CMU CL sources. It
was cleaned up and reorganized by Blaine Burks, then ported and
cleaned up more by Rob MacLachlan. Also, since the split from CMU CL,
the SBCL DESCRIBE facility was rewritten as a generic function and so
become entangled with some DESCRIBE code which was distributed as part
of PCL.

The implementation of the Mersenne Twister RNG used in SBCL is based
on an implementation written by Douglas T. Crosher and Raymond Toy,
which was placed in the public domain with permission from M.

Comments in the CMU CL version of FreeBSD-os.c said it came from
an OSF version by Sean Hallgren, later hacked by Paul Werkowski,
with generational conservative GC support added by Douglas Crosher.

Comments in the CMU CL version of linux-os.c said it came from the
FreeBSD-os.c version, morfed to Linux by Peter Van Eynde in July 1996.

Comments in the CMU CL version of backtrace.c said it was "originally
from Rob's version" (presumably Robert Maclachlan).

Comments in the CMU CL version of purify.c said it had stack direction
changes, x86/CGC stack scavenging, and static blue bag stuff (all for
x86 port?) by Paul Werkowski, 1995, 1996; and bug fixes, x86 code
movement support, and x86/gencgc stack scavenging by Douglas Crosher,
1996, 1997, 1998.

According to comments in the source files, much of the CMU CL version
of the x86 support code
was originally written by William Lott, then debugged by Paul
Werkowski, and in some cases later enhanced and further debugged by
Douglas T. Crosher; and the x86 runtime support code,
was written by Paul F. Werkowski and Douglas T. Crosher.

The CMU CL user manual (doc/cmu-user/cmu-user.tex) says that the X86
FreeBSD port was originally contributed by Paul Werkowski, and Peter
VanEynde took the FreeBSD port and created a Linux version.

According to comments in src/code/bsd-os.lisp, work on the generic BSD
port was done by Skef Wholey, Rob MacLachlan, Scott Fahlman, Dan
Aronson, and Steve Handerson.

Douglas Crosher wrote code to support Gray streams, added X86 support
for the debugger and relocatable code, wrote a conservative
generational GC for the X86 port, and added X86-specific extensions to
support stack groups and multiprocessing.

The CMU CL user manual credits Robert MacLachlan as editor. A chapter
on the CMU CL interprocess communication extensions (not supported in
SBCL) was contributed by William Lott and Bill Chiles.

Peter VanEynde also contributed a variety of #+HIGH-SECURITY patches
to CMU CL, to provide additional safety, especially through runtime
checking on various tricky cases of standard functions (e.g. MAP with
complicated result types, and interactions of various variants of

Raymond Toy wrote CMU CL's PROPAGATE-FLOAT-TYPE extension and various
other floating point optimizations. (In SBCL, the PROPAGATE-FLOAT-TYPE
entry in *FEATURES* first became SB-PROPAGATE-FLOAT-TYPE, then went
away completely as the code became an unconditional part of the

CMU CL's long float support was written by Douglas T. Crosher.

Paul Werkowski turned the Mach OS support code into Linux OS support code.

Versions of the RUN-PROGRAM extension were written first by David
McDonald, then by Jim Healy and Bill Chiles, then by William Lott.


Bill Newman did the original conversion from CMU CL 18b to a form
which could bootstrap itself cleanly, on Linux/x86 only. Although they
may not have realized it at the time, Rob Maclachlan and Peter Van
Eynde were very helpful, RAM by posting a clear explanation of what
GENESIS is supposed to be doing and PVE by maintaining a version of
CMU CL which worked on Debian, so that I had something to refer to
whenever I got stuck.


(Note: (1) This is probably incomplete, since there's no systematic
procedure for updating it. (2) Some more details are available in the
NEWS file, in the project's CVS change logs, and in the archives of
the sbcl-devel mailing list. (3) In this, as in other parts of SBCL,
patches are welcome. Don't be shy.)

Martin Atzmueller:
  He reported many bugs, fixed many bugs, ported various fixes
  from CMU CL, and helped clean up various stale bug data. (He has
  been unusually energetic at this. As of sbcl-, the
  total number of bugs involved likely exceeded 100. Since then,
  I've lost count. See the CVS logs.)

Daniel Barlow:
  He made SBCL play nicely with ILISP. He figured out how to get the
  CMU CL dynamic object file loading code to work under SBCL. He
  ported CMU CL's support for Alpha and PPC CPUs to SBCL, and then
  continued to improve the ports. He wrote code (e.g. grovel_headers.c
  and stat_wrapper stuff) to handle machine-dependence and
  OS-dependence automatically, reducing the amount of hand-tweaking
  required to keep ports synchronized. He's also provided support
  for SBCL (as well as for free Common Lisp in general) through
  his CLiki website.

Cadabra, Inc. (later merged into
  They hired Bill Newman to do some consulting for them,
  including the implementation of EQUALP hash tables for CMU CL;
  then agreed to release the EQUALP code into the public domain,
  giving SBCL (and CMU CL) its EQUALP hash tables.

Douglas Crosher:
  He continued to improve CMU CL after SBCL forked from it, creating 
  many patches which were directly applicable to SBCL. Notable examples
  include fixes for various compiler bugs, the implementation of
  CL:DEFINE-SYMBOL-MACRO, and a generalization of the type system's
  handling of the CONS type to allow ANSI-style (CONS FOO BAR) types. 

Alexey Dejneka:
  He has fixed many, many bugs. There's no single summary theme, but
  he's fixed about a dozen different bugs in LOOP alone, and more
  in the compiler itself. It appears that a lot of his fixes there
  and elsewhere reflect systematic public-spiritedness, fixing bugs
  as they show up in sbcl-devel or as archived in the BUGS file.

Nathan Froyd:
  He has fixed various bugs, and also done a lot of internal
  cleanup, not visible at the user level but important for
  maintenance. (E.g. converting the PCL code to use LOOP instead
  of the old weird pre-ANSI ITERATE macro so that the code can be
  read without being an expert in ancient languages and so that
  can delete a thousand lines of implement-ITERATE macrology.)

Matthias Hoelzl:
  He reported and fixed COMPILE's misbehavior on macros.

Espen S Johnsen:
  He provided an ANSI-compliant version of CHANGE-CLASS for PCL.

Arthur Lemmens:
  He found and fixed a number of SBCL bugs while partially porting
  SBCL to bootstrap under Lispworks for Windows

Robert MacLachlan:
  He has continued to answer questions about, and contribute fixes to, 
  the CMU CL project. Some of these fixes, especially for compiler
  problems, has been invaluable to the CMU CL project and, by
  porting, invaluable to the SBCL project as well.

Pierre Mai:
  He has continued to work on CMU CL since the SBCL fork, and also
  patched code to SBCL to enable dynamic loading of object files 
  under OpenBSD.

Eric Marsden:
  Some of his fixes to CMU CL since the SBCL fork have been ported
  to SBCL.

Dave McDonald:
  He made a lot of progress toward getting SBCL to be bootstrappable
  under CLISP.

William ("Bill") Newman:
  He continued to maintain SBCL after the fork, increasing ANSI
  compliance, fixing bugs, regularizing the internals of the
  system, deleting unused extensions, improving performance in 
  some areas (especially sequence functions and non-simple vectors),
  updating documentation, and even, for better or worse, getting
  rid of various functionality (e.g. the byte interpreter).

Christophe Rhodes:
  He ported SBCL to SPARC, made various port-related and SPARC-related
  changes (like *BACKEND-SUBFEATURES*), made many fixes and
  improvements in the compiler's type system, has done a substantial
  amount of work on bootstrapping SBCL under unrelated (non-SBCL,
  non-CMU-CL) Common Lisps, and contributed in other ways as well.

Stig Erik Sandoe:
  He showed how to convince the GNU toolchain to build SBCL in a way
  which supports callbacks from C code into SBCL.

Brian Spilsbury:
  He wrote Unicode-capable versions of SBCL's character, string, and
  stream types and operations on them.

Raymond Toy:
  He continued to work on CMU CL after the SBCL fork, especially on
  floating point stuff. Various patches and fixes of his have been
  ported to SBCL.

Peter Van Eynde:
  He wrestled the CLISP test suite into a mostly portable test suite
  (clocc ansi-test) which can be used on SBCL, provided a slew of
  of bug reports resulting from that, and submitted many other bug
  reports as well.

Colin Walters:
  His O(N) implementation of the general case of MAP, posted on the mailing list, was the inspiration for similar MAP
  code added in sbcl-0.6.8.

Raymond Wiker:
  He ported sbcl-0.6.3 back to FreeBSD, restoring the ancestral
  CMU CL support for FreeBSD and updating it for the changes made
  from FreeBSD version 3 to FreeBSD version 4. He also ported the
  CMU CL extension RUN-PROGRAM, and related code, to SBCL.

INITIALS GLOSSARY (helpful when reading comments, CVS commit logs, etc.)

AL   Arthur Lemmens
MNA  Martin Atzmueller
DB   Daniel Barlow
DTC  Douglas Crosher
APD  Alexey Dejneka
NJF  Nathan Froyd
RAM  Robert MacLachlan
WHN  William ("Bill") Newman
CSR  Christophe Rhodes
PVE  Peter Van Eynde
PW   Paul Werkowski