My first JAPH

Hiya,

This JAPH uses the properties of cyclic subgroups to generate a permutation which extracts the JAPH string out of the garbage in the first line.

For the mathematically inclined, the group is Z_29 and the generator is 2.

Kudos to the monk that finds why it doesn't work right on versions less than 5.6.0

Comments, suggestions?

$_=q+juzecsthaghyzrkiererzkntoapl+;$a=$|+
0xc0ff33-(0xf847*0xc7);sub a{%h=map{$a**
$_%qq;${a}9;=>$_}($|..qq.${a}7.);@_=values
%h;splice@_,$|,$a.(0xc0de/2/13/211/3+$a)
;}@_=unpack(qq)C*),$_);map{$_=chr$_[$_]
;s}z}\040};s!y!\012!;print;}a(m;japh\););
[download]

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Re: My first JAPH by Dominus (Parson) on Nov 21, 2000 at 00:57 UTC
I was a little disappointed that it doesn't actually depend much on the properties of Z₂₉. The main place where Z₂₉ appears is in the `a()` subroutine where you generate a hash `%h` whose keys are elements of Z₂₉ and whose values are the discrete logarithms of those elements. But then you immediately turn around and use `values` on `%h`, which extracts the logs, but not in any mathematically interesting order. The order is determined by the order in which the Z₂₉ elements happen to appear in the Perl hash, which is dependent on the hashing function that Perl uses. This is why the program doesn't work except under 5.6.0: The Perl hash function changed in 5.6.0, and the order of the items in the return value of `a()` depends on this hash function.	[reply]
Re: Re: My first JAPH by rpc (Monk) on Nov 21, 2000 at 01:58 UTC
Ah, I see. Thanks for pointing that out. I thought that it would return the order in which the elements of Z_29 were found; it seemed to on tests. I was interested in the order in which the elements were found, using exponents in ascending order. I naively thought this approach would do just that, and eliminate duplicate elements. Thanks!	[reply]
Re: My first JAPH by Dominus (Parson) on Nov 21, 2000 at 02:49 UTC
Says rpc: > I thought that it would return the order in which the elements of Z_29 were found Nope. Here's what perlfunc has to say about that: `values HASH` ... The values are returned in an apparently random order. The actual random order is subject to change in future versions of perl... so there you go.	[reply]