Talk:Fixed-point combinator: Difference between revisions

Revision as of 14:18, 11 May 2019

Revision as of 18:43, 11 May 2020

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Maybe we could try to improve it a little / make it more readable (at least add proper indendation) and then incorporate it into the article.

<sourcesyntaxhighlight lang=ruby>

y = lambda { |f| (lambda { |x| lambda { |*args| (f.call(x.call(x))).call(*args) }}).call(lambda { |x| lambda { |*args| (f.call(x.call(x))).call(*args) }})}

b = y.call(lambda { |f| lambda {|i| if i == 0 then 1 else i * (f.call(i-1)) end }})

puts(b.call 5) # 120

</syntaxhighlight>

</source>

[[User:Subwy|Subwy]] ([[User talk:Subwy|talk]]) 10:58, 10 December 2008 (UTC)

Line 182:

There are two fix point combinators in Haskell, one is code-replicating, another is through sharing:

<sourcesyntaxhighlight lang="haskell">

fix f = f (fix f)

fix f = x where x = f x

</syntaxhighlight>

</source>

The second one lends itself naturally to corecursive definitions, like

<sourcesyntaxhighlight lang="haskell">

fibs = fix ((0:) . (1:) . next)

where

next (a:t@(b:_)) = (a+b):next t

</syntaxhighlight>

</source>

Used w/ the first fix, it still works though runs in quadratic time.

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Here's a tested PHP 5.4 implementation for the Y Combinator function:

<sourcesyntaxhighlight lang=php>

function Y(callable $f)

{

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return $funcA($funcA);

}

</syntaxhighlight>

</source>

And the factorial example applied to it:

<sourcesyntaxhighlight lang=php>

$factorial = Y(

function ($fac)

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$result = $factorial(5); // 120

</syntaxhighlight>

</source>

[[User:Jazzer7|Jazzer7]] ([[User talk:Jazzer7|talk]]) 06:51, 6 June 2012 (UTC)

Line 505:

''For example, a Y-combinator implementation of factorial in the [[Wolfram Language]] would be''

<sourcesyntaxhighlight lang=ocaml>Y = Function[f, #[#]&[Function[g, f[g[g][##]&]]]];

factorial = Y[Function[f, If[# < 1, 1, # f[# - 1]] &]];

factorial[6] (*Yields 120*)</sourcesyntaxhighlight>

[[User:Thepigdog|Thepigdog]] ([[User talk:Thepigdog|talk]]) 02:20, 26 May 2015 (UTC)