Alvaro Videla on Structured Programming with Go To Statements by Donald Knuth

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Harmful GOTO's, Premature Optimizations, and Programming Myths are The Root of all Evil Alvaro Videla

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Myths

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myth: a widely held but false belief or idea Google deﬁne

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myth: an unproved or false collective belief that is used to justify a social institution dictionary.com

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The Book of Legendary Lands

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What it was that Christopher Columbus tried to demonstrate?

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A History of the Life and Voyages of Christopher Columbus

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Lactantius - Cosmas Indicopleustes

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Do we have similar myths in Computer Science?

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Some Myths • No Unit-Tests, no working code • Procedure calls are expensive • NoSQL is faster than traditional DBs • 10x Engineers • Servers are cheaper than engineers

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In the beginning…

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May I ask if there is a reason why you prefer using goto instead of function recursion? https://github.com/igorw/retry/issues/3

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retry library

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retry library

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retry library

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GOTO ﬂamewar dot gif

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Go To Statement Considered Harmful

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GOTO still considered harmful?

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A case against the goto statement + Niklaus Wirth = Go To Statement Considered Harmful

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No content

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Please don't fall into the trap of believing that I am terribly dogmatical about [the go to statement]. I have the uncomfortable feeling that others are making a religion out of it, as if the conceptual problems of programming could be solved by a single trick, by a simple form of coding discipline! E. Dijkstra

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In search of Silver Bullets • Microservices • Testing • Agile • Performance Tricks • NoSQL • Message Queues

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Beating the CAP Theorem https://www.youtube.com/watch?v=Wp08EmQtP44#t=1273

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There is no single development, in either technology or management technique, which by itself promises even one order of magnitude [tenfold] improvement within a decade in productivity, in reliability, in simplicity Frederick Brooks Jr No Silver Bullet - http://worrydream.com/refs/Brooks-NoSilverBullet.pdf

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Structured programming with go to statements • Introduction • Elimination of Go To Statements • Introduction of Go To Statements • Conclusions

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Structured programming with go to statements

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What year is this paper from?

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1974 http://www.gregwilson.co.uk/tag/muhammad-ali/

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http://dl.acm.org/citation.cfm?id=807045&dl=ACM&coll=DL

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Logic Programming http://dspace.mit.edu/handle/1721.1/6171 http://dl.acm.org/citation.cfm?doid=155360.155362 1969 1972

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http://web.archive.org/web/20120716185629/http://www.bitsavers.org/pdf/dartmouth/BASIC_Oct64.pdf

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1973: Ethernet & UNIX http://www.computerhistory.org/timeline/?year=1973

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1976: Big O Notation http://www.phil.uu.nl/datastructuren/10-11/knuth_big_omicron.pdf

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1976: Big O Notation http://www.phil.uu.nl/datastructuren/10-11/knuth_big_omicron.pdf

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1977: RSA http://www.google.com/patents/US4405829

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1978: Type Polymorphism https://courses.engr.illinois.edu/cs421/sp2013/project/milner-polymorphism.pdf

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TL;DR: 1974 • Almost no personal computers • Public Encryption a new thing • Structured Programming was all the rage • Abstract Data Types a new thing

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low computer resources

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“most of the running time in non-IO-bound programs is concentrated in about 3% of the source text” D. Knuth

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“Experience indicates that nearly everybody has the wrong idea about the real bottlenecks in his programs” D. Knuth Computer Programming as an Art - http://dl.acm.org/citation.cfm?id=361612

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“we should forget about small efﬁciencies, say about 97% of the time” D. Knuth

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“premature optimization is the root of all evil” D. Knuth

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“premature optimization is the root of all evil” D. Knuth The Godwin Law of Optimization Discussions

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“Yet we should not pass up our opportunities in that critical 3%. A good programmer will not be lulled into complacency by such reasoning, he will be wise to look carefully at the critical code; but only after that code has been identiﬁed” D. Knuth

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“the universal experience of programmers who have been using measurement tools has been that their intuitive guesses fail” D. Knuth

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more GOTO elimination with focus on performance and program readability

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“My books emphasize efﬁciency because they deal with algorithms that are used repeatedly as building blocks in a large variety of applications” D. Knuth

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“We shouldn't merely remove go to statements because it's the fashionable thing to do; the presence or absence of go to statements is not really the issue.” D. Knuth

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“We shouldn't merely remove go to statements because it's the fashionable thing to do; the presence or absence of go to statements is not really the issue.” D. Knuth

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“The question is whether we should ban it [GOTO], or educate against it” Donald Knuth

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Cargo Cult Programming http://c2.com/cgi/wiki?CargoCult

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“The biggest problem we have as human beings is that we confuse our beliefs with reality” Alan Kay http://www.tele-task.de/archive/video/html5/14029/

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How did we arrive to this status?

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Pop Culture

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“[in the 70s] computing spread out much, much faster than educating unsophisticated people can happen” Alan Kay https://queue.acm.org/detail.cfm?id=1039523

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Twitter/HackerNews Oriented Programming

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http://tinytocs.org/

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“Those who cannot remember the past are condemned to repeat it" George Santayana https://archive.org/stream/lifeofreasonorph01sant#page/284/mode/2up

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https://archive.org/stream/lifeofreasonorph01sant#page/284/mode/2up

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History Repeats Itself Agile vs. Thinking Forth http://thinking-forth.sourceforge.net

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History Repeats Itself TDD https://arialdomartini.wordpress.com/2012/07/20/you-wont-believe-how-old-tdd-is/ You won’t believe how old TDD is vs.

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History Repeats Itself offline-first http://www.isi.edu/~johnh/RESEARCH/ucla/#ficus_replication primarily-disconnected vs.

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“In 1968, the Communications of the ACM published a text of mine under the title "The goto statement considered harmful", which in later years would be most frequently referenced, regrettably, however, often by authors who had seen no more of it than its title” E. Dijkstra https://www.cs.utexas.edu/users/EWD/transcriptions/EWD13xx/EWD1308.html

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Fahreinheit 451

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“Classics cut to fit fifteen-minute radio shows, then cut again to fill a two-minute book column, winding up at last as a ten- or twelve-line dictionary resume” Fahrenheit 451

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Memes

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“[…] there has been far too much emphasis on go to elimination instead of on the really important issues; people have a natural tendency to set up all easily understood quantitative goal like the abolition of jumps, instead of working directly for a qualitative goal like good program structure” D. Knuth

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“we should strive most of all for a program that is easy to understand and almost sure to work” D. Knuth

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“we had better see to it that the computer industry does not kill computing science” E. Dijkstra https://www.cs.utexas.edu/users/EWD/transcriptions/EWD12xx/EWD1284.html

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Thanks Alvaro Videla - @old_sound