(=/`0:@.(2|#))
could be =/@:(2&{.)
but if it doesn't matter what the result is when there is one character
(as it appears to my eye), ({.=}.) would also work. Best might be to
use fill: =/"1@:(_2&(]\))
Insert-at-index is a pain, and I don't know of any better way than using #.
I spent some time thinking of a way to do this without ^:_ with no luck.
I'd like to see one.
I'm afraid to run preprocess on an input of 'xxx': it looks like a slow
way to out-of-memory.
Henry Rich
On 2/19/2011 9:16 PM, Marshall Lochbaum wrote:
> dblprocess=: (#!.'x'~ 1 j. i.@# = (2* 1 i.~ (_2 (=/`0:@.(2|#))\ ])))
> ::]^:_
> preprocess=: [: ,&'x'^:(1=2|#) dblprocess
>
> Provides a moderately blunt preprocessor. Things I'd like fixed:
> (_2 (=/`0:@.(2|#))\ ])) should just be (_2 =/\ ]) , but on an odd length
> string the last part, say (=/\ 'e') , gives a single character and not a
> Boolean, resulting in a domain error.
> Does anyone know a better way to do insertion with an index than using # ?
>
> preprocess 'allisdiscoveredflee'
> allisdiscoveredfleex
> preprocess 'xallisdiscoveredflee'
> xalxlisdiscoveredfleex
> preprocess 'xallisdiscoveredxflee'
> xalxlisdiscoveredxflexex
>
> Marshall
>
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of Henry Rich
> Sent: Saturday, February 19, 2011 1:40 PM
> To: Programming forum
> Subject: Re: [Jprogramming] Playfair cipher
>
> Oh yeah,
>
> pf =. 'paswo','rdbce','fghik','lmnqt',:'uvxyz'
>
> (thanks Ric)
>
> Henry Rich
>
> On 2/19/2011 11:39 AM, Henry Rich wrote:
>> I worked on the easy part:
>>
>> pfr =. ((] (<"1@[ { ])~ ((0 1&(|."_1)&.|:@[)`(-"1 |.)@.(+./@])
>> =/) @ ($@] #: (i.~ ,))) ];.0)~
>>
>> ; _2 pf&pfr\ 'allisdiscoveredfleex'
>> pmqfabhwewzddrrgtrbz
>>
>> ; _2 (];.0 pf)&pfr\ 'pmqfabhwewzddrrgtrbz'
>> allisdiscoveredfleex
>>
>> I can now add monad u;.0 to my Life List.
>>
>> (you would also need a preconditioner to handle double letters and
>> odd-length input).
>>
>> I was hoping the same program would work for the hard part, but I
>> wasn't sure what to do when the two letters match in more than one axis.
>>
>> Henry Rich
>>
>>
>> On 2/19/2011 7:40 AM, Kip Murray wrote:
>>> The Playfair cipher http://en.wikipedia.org/wiki/Playfair_cipher is
>>> based on a 5 by 5 character array that treats i and j as equivalent:
>>>
>>> paswo
>>> rdbce
>>> fghik
>>> lmnqt
>>> uvxyz
>>>
>>> To encode "All is discovered flee" you replace pairs of letters al li
>>> sd is co ve re df le ex with pairs diagonally opposite, one to the
>>> right, or one below (wrapping) from the table, getting
>>>
>>> pm qf ab hw ew zd dr rg tr bz
>>>
>>> Your mission, should you decide to accept it, is to write j code for
>>> enciphering and deciphering, given the five by five table. That's
>>> the easy part. The hard part is to design and implement an analogous
>>> cipher that uses the 3 by 3 by 3 character array below to replace
>>> triples of letters alx _is _di sco ver ed_ fle ex_
>>>
>>> pas
>>> wor
>>> dbc
>>>
>>> efg
>>> hij
>>> klm
>>>
>>> nqt
>>> uvx
>>> yz_
>>>
>>> ---------------------------------------------------------------------
>>> - For information about J forums see
>>> http://www.jsoftware.com/forums.htm
>>>
>> ----------------------------------------------------------------------
>> For information about J forums see http://www.jsoftware.com/forums.htm
>>
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
>
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
>
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
