the surprisingly tense history of the schwartzian transform

Alpine Perl Workshop 2016 • brian d foy

The Surprisingly Tense History of the

Schwartzian Transform

The Perl Review • www.theperlreview.com

The Surprisingly Tense History of the Schwartzian Transform

http://bit.ly/2bHNNx4



Randal Schwartz

Just another

hacker.

• troff• emacs•Lisp•Perl•Smalltalk•…



Tom Christiansen

• Languages geek • Csh god• Perl evangelist


The Surprisingly Tense History of the Schwartzian Transform The Technique

Its ExpressionThe Arguments

Its NameThe Reckoning



decoratesort

undecorate



computeassociate

sortmap



Richard Stallman

• Editor editor• GNU• Free Software



TECO - Text Editor and CorrectorEmacs - Editing MACroS EINE - E. Is Not Emacs

ZWEI - Z. Was EINE InitiallyGNU Emacs


The Surprisingly Tense History of the Schwartzian Transform Lisp

(defun schwartzian-transform (list costly-function predicate) (mapcar #'cdr

(stable-sort (mapcar (lambda (x) (cons (funcall costly-function x) x))

list) predicate :key #'car)))

(require :sb-posix)(schwartzian-transform (directory "/etc/*") (lambda (x) (sb-posix:stat-mtime (sb-posix:stat x))) #'<=)

http://codereview.stackexchange.com/a/138436/13050


The Surprisingly Tense History of the Schwartzian Transform December 16, 1994

#!/usr/bin/perlrequire 5; # new features, new bugs!print

map { $_->[0] }sort { $a->[1] cmp $b->[1] }map { [$_, /(\S+)$/] }<>;

Randal Schwartz in comp.unix.shells


The Surprisingly Tense History of the Schwartzian Transform Unfamiliar

ComplexUndocumentedHard to learn

Too cleverNew

Different


The Surprisingly Tense History of the Schwartzian Transform OMFG

AwesomeNew featuresLists of listsPower tools



Not documented



Easy to learn

Power tools


The Surprisingly Tense History of the Schwartzian Transform FMTEYEWTK

I'm not ragging on Randal, merely teasing a bit. He's just trying to be clever, and that's what he does. I'm just submitting a sample chapter for his perusal for inclusion the mythical Alpaca Book :-)

Tom Christiansen

Far More Than Everything You've Ever Wanted to Know About Sorting, http://www.perl.com/doc/FMTEYEWTK/sort.html


The Surprisingly Tense History of the Schwartzian Transform August 30, 1995

Or for possibly more efficiency, ensure that the calls only happen once per record, rather than approximately NlogN times, with the Schwartztransformation:-)

@keys = map { $_->[0] }sort { $a->[1] <=> $b->[1] or $a cmp $b }map { [ $_, datexform($foo{$_}) ] } keys %foo;

Bennett Todd in comp.lang.perl.misc

https://groups.google.com/forum/?hl=en#!topic/comp.lang.perl.misc/fLo0RNV8oW8


The Surprisingly Tense History of the Schwartzian Transform January 1996

http://www.stonehenge.com/merlyn/UnixReview/col06.html

Randal explains map-sort-map in Unix ReviewI'm going to talk about some sorts of sorts, and hopefully you'll sort everything out by the time you're finished reading. (And no, despite the similarity to my name, I will not talk about ``random sorts''.)


The Surprisingly Tense History of the Schwartzian Transform April 1996

Tom labels a benchmark "Schwartzian XFrom" in comp.lang.perl.misc for “Read directory in timestamp order?”

https://groups.google.com/d/msg/comp.lang.perl.misc/pw-Hl4byLnc/yzejRnku3RoJ


The Surprisingly Tense History of the Schwartzian Transform July 1996

https://groups.google.com/d/msg/comp.lang.perl.misc/6NEeX4XJx54/nmpMmReMIbcJ

Colin Howarth in comp.lang.perl.misc

"Schwartzian transform of %$self ... help?"


The Surprisingly Tense History of the Schwartzian Transform October 1996

Tom posts a draft of perllol with "Schwartzian Transform"


The Surprisingly Tense History of the Schwartzian Transform December 1996

https://groups.google.com/d/msg/comp.lang.perl.misc/fPx42DB2jd8/cC_6osV70mMJ

Tom in comp.lang.perl.misc

I'm still pissed at Randal for having posted it, especially the way he did.



I hereby propose that the aforementioned Lispism, yclept “Schwartzian Transform", be recast in a less Teutonic albeit darker light; to wit, "Black Transform", as this spelling more accurately connotes its sinister subtleties. :-)

Tom later in the same thread


The Surprisingly Tense History of the Schwartzian Transform December 1996

I wonder if this chunk of code will haunt us forever.

Eric Arnold in comp.lang.perl.misc

https://groups.google.com/d/msg/comp.lang.perl.misc/fPx42DB2jd8/CTRmyWyJW6MJ


The Surprisingly Tense History of the Schwartzian Transform 1999


The Surprisingly Tense History of the Schwartzian Transform Orcish Manuever

@sorted = sort {( $times{$a} ||= -M $a ) <=>( $times{$b} ||= -M $b )

} @old_array;

Perl 4 compatible version


The Surprisingly Tense History of the Schwartzian Transform 2000


The Surprisingly Tense History of the Schwartzian Transform Python 2.4, 3

sorted = sorted(string_list, key=…)

string_list.sort(key=lambda …)

map(lambda x: x[1], sorted( map(lambda x: (f(x), x), old_list)))

new_list = zip(* sorted( zip(map(f, old_list), old_list)))[1]


The Surprisingly Tense History of the Schwartzian Transform Python 2

tmp2 = [ (int(s[10:15]), s) for s in L ] tmp2.sort()Isorted = [ x[1] for x in tmp2 ]

sorted([5, 2, 4, 1, 3], cmp=…)


The Surprisingly Tense History of the Schwartzian Transform Ruby

[1,1.1,1.2,10].sort_by {|n| n.to_s}



•Innsbruck - CC BY 2.0 by Reisender1701 (Flickr) https://goo.gl/PuILnA

•Randal Schwartz - CC BY-SA 3.0 by Chris Marquardt https://commons.wikimedia.org/wiki/File:Randal_Schwartz_headshot_by_Chris_Marquardt.png

•Tom Christiansen - CC BY-SA 3.0 by Tim Bray https://en.wikipedia.org/wiki/File:Tom_Christiansen_in_2008.jpg

•Richard Stallman - CC BY-SA 3.0 by Thesupermat https://commons.wikimedia.org/wiki/File:Richard_Stallman_-_Fête_de_l%27Humanité_2014_-_010.jpg

the surprisingly tense history of the schwartzian transform

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