Well, let me give you my final version then:
levdist=: 4 : 0"1
'a b'=. (/: #&>)x;y
z=. >: iz =. i.#b
for_j. a do.
z=. <./\&.(-&iz) (>: <. (j ~: b) + |.!.j_index) z
end.
{:z
)
No way is this ever going to be a J primitive. And J does not allow
overloading primitive names with user code. You'll have to give it a
name and use it.
I've not heard of Tanimoto distance, but we can work on that next.
Henry Rich
Jan Jacobs wrote:
> Henry,
> very good. For longer strings it is more than double so fast as the previous
> version. In my test cases it even consumes less memory.
> Is it possible to include this as a native function in J (e.g. overloading
> -. or s:)?
> Same question but now for Tanimoto distance?
> Jan.
>
>
> On 12/19/09, R.E. Boss <r.e.b...@planet.nl> wrote:
>> Smart analysis. Chapeau!
>>
>>
>> R.E. Boss
>>
>>
>> -----Oorspronkelijk bericht-----
>> Van: programming-boun...@jsoftware.com
>> [mailto:programming-boun...@jsoftware.com] Namens Henry Rich
>> Verzonden: zaterdag 19 december 2009 3:00
>> Aan: Programming forum
>> Onderwerp: [Jprogramming] Levenshtein distance
>>
>> I was working with R. E.'s compact implementation of the Levenshtein
>> distance and I found an interesting equivalence:
>>
>> (<. >:)/\.&.|.
>>
>> can be replaced by
>>
>> (<./\@:- + ]) i...@#
>>
>> which uses a little more space but is quite a bit faster for large
>> operands. So now I have the version:
>>
>> NB. Levenshtein distance between two strings
>> levdist=: 4 : 0
>> 'a b'=. (/: #&>)x;y
>> z=. i.>:#b
>> for_j. a do.
>> z=. ((<./\@:- + ]) i...@#) ((j ~: b) + }:z) ({...@] , (<. }.)) >:z
>> end.
>> {:z
>> )
>>
>>
>> Henry Rich
>> ----------------------------------------------------------------------
>> 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
