Loops/For: Difference between revisions

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Revision as of 18:02, 10 August 2022

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→‎{{header|APL}}: Improve nested version portability; add tradfn version with :for

Markjreed

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Revision as of 07:55, 9 August 2022 (view source) Amanvir (talk \| contribs) (Simple for loop in Rapira) ← Older edit		Revision as of 18:02, 10 August 2022 (view source) Markjreed (talk \| contribs) (→‎{{header\|APL}}: Improve nested version portability; add tradfn version with :for) Newer edit →
Line 369: =={{header\|APL}}== ~~The~~For most purposes, the APL analogue of a for loop is the '''each''' operator <tt>¨</tt>. The most natural way to accomplish this task doesn't use a nested '''each''', but the '''repeat''' operator <tt>/</tt> inside a single '''each''': <lang APL>stars ← {~~⎕←⍵~~ ⍵ 1 ⍴ {⍵/''}¨⍳5⍳⍵ }</lang> ~~However, to~~To stick to the letter of the task description, we can nest an '''each''' inside another one., ~~This becomes less portable as~~but it ~~relies on '''⎕ucs''~~' ~~to generate~~s a ~~newline, assumes that newline is character 10, and requires support for multiple statements inside an anonymous function (dfn, <tt>{</tt> ... <tt>}</tt>), which e.g. GNU APL does not~~little ~~have~~silly: <lang APL>stars ← { ⍵ 1 ⍴ { {''} ¨ ⍳⍵} ¨ ⍳⍵ }</lang> Additionally, Dyalog and some other dialects support the more traditional structured programming controls inside a named function definition (tradfn): {{works with\|Dyalog APL}} <lang APL>∇result ← stars count; i; j; vec ~~<lang APL>{_←{⍞←''}¨⍳⍵ ⋄ ⍞←⎕ucs 10}¨⍳5</lang>~~ vec ← ⍬ :for i :in ⍳ count vec ,← ⊂'' :for j :in ⍳ i vec[i],←'' :endfor :endfor result ← count 1 ⍴ vec ∇</lang> {{Out}} The result of all three implementations of `stars` is a column vector, which is displayed like this: ~~The output of both versions is the same:~~ <pre>* stars 5 * *