[Jprogramming] Verb definition + inadvertent train formation.

[Henry Rich]

Did you try |: with boxed x?

    (<0 1) |: i. 4 4
0 5 10 15

Henry Rich



On 11/18/2012 8:51 PM, Don & Cathy Kelly wrote:
> This also helped me where I wanted to extract the diagonal elements of
> an array!
> I was trying for a neater way to do it but as in the end,  I have to do
> it several times, it appears that it is easier to establish a unit
> matrix and then use this  each time I want to deal with a matrix of the
> same size
> rather than using (*  =@i.@#) y  and repeating for different y  or using
> the cap as you suggest, I can simply define a unit matrix U
> and then us U*y as needed.
>
> Still very hit and miss on the multiple ways to skin a cat in J
>
> Don Kelly
>
>
>
> On 15/11/2012 9:55 PM, bob therriault wrote:
>> Hey Vijay,
>>
>> Nothing wrong with a novice question, especially when it is so clearly
>> phrased.
>>
>> Take a look at these examples and see if this gives you some ideas.
>>
>> fact1=: */@:>:@:i.
>>     fact1 5
>> 120
>>     fact2=: [:*/>:@:i.
>>     fact2 5
>> 120
>>     fact3=: [:*/[:>:i.
>>     fact3 5
>> 120
>>
>> You want to have the verbs act sequentially on the argument and your
>> original definition is a fork which has the outside verbs act on the
>> argument and then send the results to the left and the right of the
>> centre verb.
>> (v1 v2 v3) y is actually ((v1 y) v2 (v3 y)). In this case (*/ >: i.) 5
>> becomes ((*/ 5) >: (i. 5)) and then (5 >: 0 1 2 3 4) which becomes 1 1
>> 1 1 1
>>
>> A  good reference link would be
>> http://www.jsoftware.com/jwiki/Guides/Language%20FAQ#Guides.2FLanguage_FAQ.2FSentence_Train.Why_.2B-.2F_.2A:_a_works.2C_but_when_I_say_foo_.3D:_.2B-.2F_.2A:.2C_foo_a_doesn.27t_work.3F
>>
>>
>> Hope this helps. There is a lot to this language, even when you have
>> been playing with it for a while, so keep at it.
>>
>> Cheers, bob
>>
>> On 2012-11-15, at 9:20 PM, Vijay Lulla wrote:
>>
>>> Please forgive me for asking a novice question.
>>>
>>> I tried
>>> */>:i.5   NB. results in 120
>>>
>>> But I define
>>> fact=: */>:i.
>>> fact 5  NB. results in 1 1 1 1 1
>>>
>>> I remember reading about this somewhere but I cannot seem to find the
>>> relevant pages now. Any pointers as to where I could find these
>>> documents
>>> or a brief explanation (which can be easily remembered) will be very
>>> helpful and is highly appreciated.
>>> Thanks,
>>> Vijay Lulla.
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>
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