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␈↓ ↓H␈↓↓␈↓ ∧oAcknowledgements

␈↓ ↓H␈↓This␈αbook␈αbegan␈αinformally␈αat␈αUCLA␈αin␈α1970␈αas␈αan␈αalternative␈αto␈αthe␈αdata␈αstructures␈αcourse.␈αAny
␈↓ ↓H␈↓book␈αwhich␈αtakes␈αsix␈αyears␈αto␈αcomplete␈α
must␈αhave␈αa␈αlist␈αof␈αacknowledgements.␈α Between␈α
 the␈α1970
␈↓ ↓H␈↓manuscript␈α
and␈α
the␈α
 present␈αversion␈α
stretches␈α
an␈α
incredible␈αlist␈α
of␈α
revisions␈α
and␈α
rewritings.␈α That
␈↓ ↓H␈↓task␈α∪was␈α∪made␈α∀possible␈α∪only␈α∪by␈α∀the␈α∪document␈α∪preparation␈α∀system␈α∪at␈α∪the␈α∀Stanford␈α∪Artificial
␈↓ ↓H␈↓Intelligence␈α⊃Laboratory.␈α⊂ The␈α⊃artificial␈α⊂intelligence␈α⊃community␈α⊂is␈α⊃still␈α⊂the␈α⊃superior␈α⊃developer␈α⊂of
␈↓ ↓H␈↓computer related tools.

␈↓ ↓H␈↓The␈α∞final␈α
shape␈α∞of␈α∞this␈α
book␈α∞has␈α∞been␈α
guided␈α∞by␈α∞many␈α
sources,␈α∞but␈α∞particularly␈α
I␈α∞would␈α∞like␈α
to
␈↓ ↓H␈↓mention␈α Michael␈αBurke␈αand␈α the␈αSan␈αJose␈αState␈αMathematics␈αDepartment,␈αwho␈αallowed␈αme␈αto␈αuse
␈↓ ↓H␈↓my␈αmanuscript␈αin␈α
their␈αdata␈αstructures␈α
course.␈α To␈αNancy␈αMeller␈α
of␈αthe␈αUCLA␈α
Computer␈αScience
␈↓ ↓H␈↓Department␈αfor␈α
typing␈αthe␈αorginal␈α
LISP␈αnotes.␈α
 To␈αLes␈αEarnest␈α
of␈αthe␈αStanford␈α
A.I.␈αLabs␈α
for␈αaid
␈↓ ↓H␈↓beyond␈α
the␈α
call␈α
of␈α
duty.␈α To␈α
Jim␈α
Duley␈α
of␈α
Hewlett-Packard␈αfor␈α
persisting.␈α
 To␈α
Paulette␈α
for␈αtrying␈α
to
␈↓ ↓H␈↓understand.␈α⊂To␈α⊃Richard␈α⊂Manuck␈α⊂of␈α⊃the␈α⊂Stanford␈α⊂Computer␈α⊃Science␈α⊂ Library,␈α⊂a␈α⊃most␈α⊂excellent
␈↓ ↓H␈↓librarian␈α∞with␈α∞an␈α∞exceptional␈α∞library.␈α∞ To␈α∞John␈α∞McCarthy␈α∞for␈α∞ the␈α∞insight␈α∞ which␈α∞lead␈α∞to␈α∞LISP,
␈↓ ↓H␈↓and␈α for␈α
establishing␈αan␈α
environment␈αat␈αStanford␈α
which␈αis␈α
 staffed␈αso␈α
admirably␈αand␈αsupplied␈α
with
␈↓ ↓H␈↓so many talented people.

␈↓ ↓H␈↓Particular␈αmention␈αmust␈αgo␈αto␈α Guy␈αSteele,␈αwho␈αreviewed␈αa␈αmuch␈αinferior␈αversion␈αof␈αthis␈αtext.␈αHis
␈↓ ↓H␈↓insights,␈αcomments,␈αand␈αcriticisms␈αwere␈α invaluable.␈αWith␈αcomments␈αlike:␈α"that's␈αnot␈α
a␈αcompromise,
␈↓ ↓H␈↓it's a bloody surrender!", the text was bound to improve.

␈↓ ↓H␈↓Several␈α∂other␈α⊂people␈α∂have␈α∂had␈α⊂significant␈α∂influence␈α⊂on␈α∂the␈α∂text.␈α⊂I␈α∂feel␈α∂fortunate␈α⊂to␈α∂ be␈α⊂able␈α∂to
␈↓ ↓H␈↓acknowledge␈α~these␈α~individuals.␈α~D. Bruce Anderson,␈α~Bob Boyer,␈α~Michael Clancy,␈α→Bob Doran,
␈↓ ↓H␈↓Daniel Friedman,␈α0Richard Gabriel,␈α0Michael Gordon,␈α1Patrick Greussay,␈α0Anthony Hearn,
␈↓ ↓H␈↓Freidrich von Henke,␈α∩Forrest Howard,␈α∩Bill McKeeman,␈α∩Peter Milne,␈α∩J␈α∪S. Moore,␈α∩Jorge Morales,
␈↓ ↓H␈↓Steve Russell,␈α⊗Hanan Samet,␈α⊗Vic Scheinman,␈α∃Herbert Stoyan,␈α⊗Dennis Ting,␈α⊗and Steve Ward.␈α∃I
␈↓ ↓H␈↓apologize to any individuals I neglected to mention; I must surely have forgotten someone.

␈↓ ↓H␈↓Similarly␈α
there␈α∞are␈α
topics␈α
 related␈α∞to␈α
LISP␈α
which␈α∞I␈α
have␈α
neglected.␈α∞ The␈α
whole␈α
area␈α∞of␈α
Artificial
␈↓ ↓H␈↓Intelligence␈αapplications␈αhas␈αbeen␈αslighted,␈αbut␈αfor␈αevery␈αauthor␈αthere␈αmust␈αcome␈αa␈αtime␈αwhen␈αyou
␈↓ ↓H␈↓have␈αto␈αsay␈α
"Enough!".␈α I've␈αbeen␈α
saying␈αthat␈αfor␈α
several␈αyears.␈αIt␈α
is␈αparticularly␈αdifficult␈α
to␈α cease
␈↓ ↓H␈↓when␈αdealing␈αwith␈αa␈αtopic␈α
as␈α dynamic␈αas␈αLISP.␈αMany␈α
sections␈αonly␈αhint␈αat␈αdeeper␈α
problems,␈αand
␈↓ ↓H␈↓surely some errors persist; but "Enough!".

␈↓ ↓H␈↓As␈α
always␈α∞it␈α
is␈α∞the␈α
author's␈α∞responsibility␈α
for␈α
the␈α∞final␈α
shape␈α∞of␈α
a␈α∞document;␈α
the␈α∞substantial␈α
and
␈↓ ↓H␈↓textual␈α⊂errors,␈α⊂errors␈α∂of␈α⊂omission␈α⊂and␈α⊂commission␈α∂are␈α⊂all␈α⊂mine.␈α∂Each␈α⊂of␈α⊂the␈α⊂reviewers␈α∂objected
␈↓ ↓H␈↓strongly␈α
to␈α
one␈α
or␈αmore␈α
facets␈α
of␈α
this␈α
book;␈αto␈α
some,␈α
it␈α
was␈α
too␈αtheoretical;␈α
for␈α
some,␈α
too␈α practical.␈α
 I
␈↓ ↓H␈↓must have done something right.













␈↓ ↓H␈↓α␈↓ βxTo my parents, John & Esther Allen
␈↓ ↓H␈↓α␈↓ βx␈↓ ¬_To my wife and friend, Ruth E. Davis
␈↓ ↓H␈↓α␈↓ βx␈↓ ¬_␈↓ ε8To my sons, Christopher & Geoffrey.