[Jprogramming] @ and @: (atop and at)

[Raul Miller]

(Actually, no - it has to do with execution order and, of course, rank
- parsing is the first step of execution in J, but I didn't think that
one through properly.)

Thanks,

-- 
Raul


On Fri, Jan 22, 2016 at 11:03 AM, Raul Miller <rauldmiller at gmail.com> wrote:
> Order is important.
>
> Do you see why?
>
> (Hint: it has to do with implicit parenthesis provided by parsing.)
>
> Thanks,
>
> --
> Raul
>
>
> On Fri, Jan 22, 2016 at 10:55 AM, Brian Schott <schott.brian at gmail.com> wrote:
>> [Sorry, that was a mistake. This is a resend]
>>
>>    #@:>@:;:'a man a plan a canal'     NB. 1
>> 6
>>    #@:>@;:'a man a plan a canal'     NB. 2
>> 6
>>    #@>@;:'a man a plan a canal'     NB. 3
>> 1 3 1 4 1 5
>>    #@>@:;:'a man a plan a canal'     NB. 4
>> 1 3 1 4 1 5
>>    #@(>@:;:)'a man a plan a canal'     NB. 5
>> 6
>>    #@(>@;:)'a man a plan a canal'     NB. 6
>> 6
>>
>> These examples are hard for me to grok.
>> Comparing 1 and 2 and 4 suggests that either order is important or that #
>> is effected and > is not.
>> Example 6 suggests that parentheses can produce results like @: especially
>> when compared with 2.
>>
>> My experience in the past has been especially puzzling when I try to
>> combine atop with the MIDDLE TINE result of a fork as the following
>> examples attempt to cover. In these example I use at and atop in the names
>> to reflect the use of @ and @: ; I use app in the names to reflect the use
>> of append . These examples especially the comparison between the
>> application of meanatop and meanatopapp, clarify to me that atop uses the
>> rank of its predecessor (%
>>
>>    mean i. 3 4
>> 4 5 6 7
>>    meanat =: +/ #@% #
>>    meanat i. 3 4
>> 1 1 1 1
>>    meanatop =: +/ #@:% #
>>    meanatop i. 3 4
>> 4
>>    meanatapp =: +/ #@,@% #
>>    meanatapp i. 3 4
>> 1 1 1 1
>>    meanatopapp =: +/ #@:,@% #
>>    meanatopapp i. 3 4
>> 1 1 1 1
>>    meanatopappparen =: +/ #@(,@%) #
>>    meanatopappparen i. 3 4
>> 1 1 1 1
>>    meanatappparen =: +/ #@:(,@%) #
>>    meanatappparen i. 3 4
>> 4
>>
>>
>> On Fri, Jan 22, 2016 at 4:50 AM, Linda A Alvord <lindaalvord at verizon.net>
>> wrote:
>> I think I finally understand the difference!
>>
>>     A=:'a man a plan a canal'
>>    ;:A
>> ┌─┬───┬─┬────┬─┬─────┐
>> │a│man│a│plan│a│canal│
>> └─┴───┴─┴────┴─┴─────┘
>>    f=: 13 :'#>;:y'
>>    g=: 13 :'#@>;:y'
>>    h=: 13 :'#@:>;:y'
>>
>>
>> --
>> (B=) <-----my sig
>> Brian Schott
>> ----------------------------------------------------------------------
>> For information about J forums see http://www.jsoftware.com/forums.htm