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John Scholes' Conway's Game of Life: Difference between revisions
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John Scholes' Conway's Game of Life (view source)
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Perhaps the most famous APL video is [[John Scholes]] explaining his own implementation of [[Conway's Game of Life]] in [[Dyalog APL]].<ref>[[John Scholes|Scholes, John]]. [https://www.youtube.com/watch?v=a9xAKttWgP4 "Conway's Game of Life in APL"]. 2009-01-26.</ref> Scholes | Perhaps the most famous APL video is [[John Scholes]] explaining his own implementation of [[Conway's Game of Life]] in [[Dyalog APL]].<ref>[[John Scholes|Scholes, John]]. [https://www.youtube.com/watch?v=a9xAKttWgP4 "Conway's Game of Life in APL"]. 2009-01-26.</ref> In the video, Scholes develops the following [[dfn]] one step at a time: | ||
<source lang=apl> | |||
life ← {⊃1 ⍵ ∨.∧ 3 4 = +/ +⌿ ¯1 0 1 ∘.⊖ ¯1 0 1 ⌽¨ ⊂⍵} | |||
</source> | |||
Scholes also published notes<ref>[[John Scholes|Scholes, John]]. [http://dfns.dyalog.com/n_life.htm life] in the [[dfns workspace]].</ref> on the Game of Life, including alternate implementations, in his [[dfns workspace]]. The workspace includes a function which differs in a few small details. | |||
<source lang=apl> | <source lang=apl> | ||
Life←{↑1 ⍵∨.∧3 4=+/,¯1 0 1∘.⊖¯1 0 1∘.⌽⊂⍵} | Life←{↑1 ⍵∨.∧3 4=+/,¯1 0 1∘.⊖¯1 0 1∘.⌽⊂⍵} | ||
</source> | </source> | ||
In this page we will break down the function to see how each part operates. If you're completely new to APL, you probably won't understand all of it right away—consider also reading some [[Simple examples]] or APL [[introductions]]. However, you should be able to follow the general ideas. Bear in mind that APL evaluates expressions from [[Evaluation order|right to left]] unless you use parentheses. | In this page we will break down the function <source lang=apl inline>Life</source> to see how each part operates. If you're completely new to APL, you probably won't understand all of it right away—consider also reading some [[Simple examples]] or APL [[introductions]]. However, you should be able to follow the general ideas. Bear in mind that APL evaluates expressions from [[Evaluation order|right to left]] unless you use parentheses. | ||
The code here is written for [[Dyalog APL]]. It also works in [[ngn/apl]], and other [[Nested array theory|nested]] array languages allow similar implementations: see [[#Translations]]. | The code here is written for [[Dyalog APL]]. It also works in [[ngn/apl]], and other [[Nested array theory|nested]] array languages allow similar implementations: see [[#Translations]]. | ||
In 2021, Conor Hoekstra remade the video with additional explanations.<ref>Hoekstra, Conor. [https://www.youtube.com/watch?v=pMslgySQ8nc APL + Game of Life = ❤️] in the [https://www.youtube.com/channel/UC1kBxkk2bcG78YBX7LMl9pQ code_report YouTube channel]. 2021-04-25.</ref> | |||
== The Glider == | == The Glider == | ||
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=== Visualising it === | === Visualising it === | ||
To make the pattern easier to see, we can use [[indexing]] to place a <source lang=apl inline>⌺</source> symbol where there's a cell and a <source lang=apl inline>·</source> otherwise, for example: | To make the pattern easier to see, we can use [[Bracket indexing|indexing]] to place a <source lang=apl inline>⌺</source> symbol where there's a cell and a <source lang=apl inline>·</source> otherwise, for example: | ||
<source lang=apl> | <source lang=apl> | ||
Show←{'·⌺'[⎕IO+⍵]} | Show←{'·⌺'[⎕IO+⍵]} | ||
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grid ← glider⍢(¯3 ¯3∘↑) 10 10⍴0 ⍝ This works | grid ← glider⍢(¯3 ¯3∘↑) 10 10⍴0 ⍝ This works | ||
</source> | </source> | ||
=== Ruby === | |||
Github user zverok has translated Scholes' dfn to [[wikipedia:Ruby (programming language)|Ruby]] by first creating an <source lang=ruby inline>apl</source> module to implement parts of APL. The code is shown [https://github.com/zverok/ruby_as_apl on Github] and explained [https://zverok.github.io/blog/2020-05-16-ruby-as-apl.html on zverok's blog]. | |||
== Performance == | == Performance == | ||
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== References == | == References == | ||
<references /> | <references /> | ||
[[Category:Examples]][[Category:Dyalog APL examples]] | |||