Here's how I express the identity ([: f g) -: f@:g (admittedly the following
is not much use to a newcomer)
comp =: 2 : ' ([: u v) -: u @: v '
*: comp % 1 2 3
1
1 2 3 *: comp % 4 5 6
1
--Kip
Sent from my iPad
> On Mar 1, 2014, at 11:16 PM, Roger Hui <[email protected]> wrote:
>
> It's like asking where are the oxygen molecules in the air you breathe.
>
> f=: +/@i. = 2&!
> f"0 i.20
> 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
>
> See also *A Letter from Dijkstra on APL
> <http://archive.vector.org.uk/art10501260> .*
>
>
>
>
>
>
>> On Sat, Mar 1, 2014 at 7:55 PM, km <[email protected]> wrote:
>>
>> One "identity" in J is that ([: f g) -: f@:g (always returns 1). What
>> are some others?
>>
>> --Kip Murray
>>
>> Sent from my iPad
>>
>>> On Mar 1, 2014, at 8:41 PM, Raul Miller <[email protected]> wrote:
>>>
>>> Two languages which go even more heavily into "proof" territory are (if I
>>> recall correctly) Agda, and Coq.
>>>
>>> They also have some interesting aspects that I would like to see in a "J
>>> subset compiler".
>>>
>>> Thanks,
>>>
>>> --
>>> Raul
>>>
>>>
>>> On Sat, Mar 1, 2014 at 8:30 PM, David Lambert <[email protected]
>>> wrote:
>>>
>>>> Mentioning "proof" in j conversation rolls easily off the pen. Not so
>>>> with other computer languages I've used.
>>>>
>>>> (,&#~.) HASHES NB. prove the hashes are unique. (tallies agree)
>>>> 6 6
>>>>
>>>> http://forums.devshed.com/showpost.php?p=2927271&postcount=4
>>>> ----------------------------------------------------------------------
>>>> 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
> ----------------------------------------------------------------------
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