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The Ackermann function is a classic recursive example in computer science.


head

L<http://rosettacode.org/wiki/Ackermann_function#Raku>


item

code

=begin code :lang<raku>
use v6;



sub A(Int $m, Int $n) {

    $m == 0  ??    $n + 1                   !!
    $n == 0  ??  A($m - 1, 1            )   !!
                 A($m - 1, A($m, $n - 1));

}
A(1, 2).say;

# vim: expandtab shiftwidth=4 ft=perl6

=end code


root

100 Doors


100-doors.pl

24 game


24-game.pl

Accumulator factory


accumulator-factory.pl

Arbitrary-precision integers (included)


arbitrary-precision-integers.pl

Balanced brackets


balanced-brackets.pl

Binomial Coefficient


binomial-coefficient.pl

Copy a string


copy-a-string.pl

Create a two-dimensional array at runtime


create-a-two-dimensional-array-at-runtime.pl

Hailstone sequence


hailstone-sequence.pl

Last fridays of the year


last-fridays-of-year.pl

Prime decomposition


prime-decomposition.pl

README.md

para

L<Examples| file:../examples/index.podlite>


L<Download |file:../download/index.podlite>


React

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=para L<Documentation|/doc/introduction>
=para L<Modules| /mods>
=para L<Examples| file:../examples/index.podlite>
=para L<Download |file:../download/index.podlite>
=para L<About|file:../about/index.podlite>
=para 🔍 K<⌘K>/K<ctrl-K>
=end React


HEADER

FOOTER

Ackermann function


Using the in-built capabilities of your language, calculate the integer
value of:


Confirm that the first and last twenty digits of the answer are:
62060698786608744707...92256259918212890625


Find and show the number of decimal digits in the answer.


L<http://rosettacode.org/wiki/Arbitrary-precision_integers_(included)#Raku>


=begin code :lang<raku>
use v6;



my $x = ~[**] 5, 4, 3, 2;
say "5**4**3**2 = {substr($x,0,20)}...{substr($x,$x.chars-20)} and has {$x.chars} digits";

# vim: expandtab shiftwidth=4 ft=perl6

=end code


ackermann-function.pl

A problem posed by Paul Graham is that of creating a function that takes a
single (numeric) argument and which returns another function that is an
accumulator. The returned accumulator function in turn also takes a single
numeric argument, and returns the sum of all the numeric values passed in so
far to that accumulator (including the initial value passed when the
accumulator was created).


The detailed rules are at L<http://paulgraham.com/accgensub.html> and are
reproduced here for simplicity (with additions).


If after the example, you added the following code (in a made-up language)
where the factory function is called foo:


It should print 8.3. (There is no need to print the form of the accumulator
function returned by foo(3); it's not part of the task at all.)


The purpose of this task is to create a function that implements the
described rules. It need not handle any special error cases not described
above. The simplest way to implement the task as described is typically to
use a closure, providing the language supports them.


L<http://rosettacode.org/wiki/Accumulator_factory#Raku>


=begin code :lang<raku>
use v6;




sub accum ($n is copy) { sub { $n += $^x } }

my $a = accum 5;
$a(4.5);
say $a(.5);   # Prints "10".

# vim: expandtab shiftwidth=4 ft=perl6

=end code


The Raku Knowledge Base


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    =item2 L<Try Raku|https://glot.io/new/raku>
    =item2 L<Raku cheat sheet|https://github.com/Raku/mu/blob/master/docs/Perl6/Cheatsheet/cheatsheet.txt>
    =item2 L<empty|#>
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    =item2 L<Type Reference| file:../doc/types.podlite>
    =item2 L<Miscellaneous| file:../doc/miscellaneous.podlite>
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    =item2 L<Community|/doc/language/community>
    =item2 L<The list of all documents|file:../doc/index.podlite>

=item1 B<Resources>
    =item2 L<The Raku Guide|https://raku.guide/>
    =item2 L<Books |https://perl6book.com/>
    =item2 L<Rosetta Code | https://www.raku.org/community/rosettacode>

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    =item2 L<Books |https://perl6book.com/>
    =item2 L<Rosetta Code | https://www.raku.org/community/rosettacode>
    =item2 L<Learn Raku in Y minutes|https://learnxinyminutes.com/docs/raku/>
    =item2 L<Golfing |https://github.com/AlexDaniel/raku-golf-cheatsheet>
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=item1 B<Explore>
    =item2 L<Raku Blog Aggregator|https://planet.raku.org/>
    =item2 L<Rakudo Weekly|https://rakudoweekly.blog/>
    =item2 L<The Weekly Challenge |https://perlweeklychallenge.org/>
    =item2 L<Raku Advent Calendar|https://raku-advent.blog/>
    =item2 L<empty|#>
    =item2 L<empty|#>
    =item2 L<empty|#>
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=end nested
=end React


=begin React :component<CookieConsent> :id<CookieConsent> :buttonCaption("Got it!")
=para
This website uses cookies for analytics.
=end React


Ackermann function

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