List comprehensions: Difference between revisions
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===horizontal list=== |
===horizontal list=== |
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<lang rexx>/*REXX program shows a horizontal list of Pythagorean triples up to a specified number. */ |
<lang rexx>/*REXX program shows a horizontal list of Pythagorean triples up to a specified number. */ |
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parse arg n . /* |
parse arg n . /*obtain optional argument from the CL.*/ |
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if n=='' | n=="," then n= 100 /*Not specified? Then use the default.*/ |
if n=='' | n=="," then n= 100 /*Not specified? Then use the default.*/ |
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do k=1 for n; @.k= k*k /*precompute the squares of usable #'s.*/ |
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end /*k*/ |
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| ⚫ | |||
say 'Pythagorean triples (a² + b² = c², c ≤' n"):" /*display the list's title. */ |
say 'Pythagorean triples (a² + b² = c², c ≤' n"):" /*display the list's title. */ |
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$= /*assign a null to the triples list. */ |
$= /*assign a null to the triples list. */ |
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do a=1 |
do a=1 for n-2; bump= a//2 /*Note: A*A is faster than A**2. */ |
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do |
do b=a+1 to n-1 by 1+bump |
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ab= @.a + @.b /*AB: a shortcut for the sum of A² & B²*/ |
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if bump==0 & b//2==0 then cump= 2 |
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else cump= 1 |
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do c=b+cump to n by cump |
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if ab<@.c then leave /*Too small? Then try the next B. */ |
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if ab==@.c then do; $=$ '{'a"," || b','c"}"; leave; end |
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end /*c*/ |
end /*c*/ |
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end /*b*/ |
end /*b*/ |
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end /*a |
end /*a*/ |
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#= words($) |
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| ⚫ | |||
do j=1 until p==0; p= lastPos('}', $, sw) /*find the last } */ |
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if p\==0 then do; _= left($, p) |
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say; say # 'members listed.' /*triples are listed in order of 1st #.*/</lang> |
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say strip(_) |
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$= substr($, p+1) |
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end |
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end /*j*/ |
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say strip($) |
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say |
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say # ' members listed.' /*stick a fork in it, we're all done. */</lang> |
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{{out|output|text= when using the following input: <tt> 35 </tt>}} |
{{out|output|text= when using the following input: <tt> 35 </tt>}} |
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<pre> |
<pre> |
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