[Jprogramming] Newbie question

[Ricardo Forno]

This seems to be my case, ha ha!
I am now retired, but in the 70's I used APL a lot.
----- Original Message ----- 
From: "Björn Helgason" <gosinn at gmail.com>
To: "Programming forum" <programming at jsoftware.com>
Sent: Friday, November 04, 2011 12:39 PM
Subject: Re: [Jprogramming] Newbie question


>I guess it takes a long time for anyone to realize the power of rank.
>
> https://groups.google.com/forum/?hl=is#!searchin/j-programming/rank/j-programming/XwvPm9UhCt8/lMyXcnT_6wIJ
>
> Some people claim that if you do not understand rank you do not
> understand J
>
> 2011/11/4 Roger Hui <rogerhui.canada at gmail.com>
>
>> When "table" x f/y was introduced (at the very beginning) we did not
>> fully comprehend the power of the rank operator.  If I had realized
>> that table was just x f"(lr,_) y, where lr is the left rank of f, I
>> might have tried to argue strongly for using the dyad f/ for something
>> else.
>>
>>
>>
>> On Fri, Nov 4, 2011 at 2:15 AM, Henry Rich <HenryHRich at nc.rr.com> wrote:
>> > Just a quibble with terminology: 'item' means _1-cell.  That concept
>> > does not apply here.  If you define 'l-cell' to be the left rank of the
>> > verb, and 'r-cell' the right rank, you could say
>> >
>> > ...it loops through all the l-cells of x, then for each of those, all
>> > the r-cells of y...
>> >
>> > Henry Rich
>> >
>> > On 11/4/2011 12:13 AM, Marshall Lochbaum wrote:
>> >> * has rank 0 already, so it isn't necessary. The definition of / is
>> that it
>> >> applies the verb with rank (left rank),_ . Essentially, this means 
>> >> that
>> it
>> >> loops through all the items of x, then for each of those, all the 
>> >> items
>> of
>> >> y, where an "item" is an item with the left rank of the verb. If you 
>> >> try
>> >> magic/~ a with magic having rank _ (because it's a fork), you just get
>> (a
>> >> magic"_ _"_ _ a), which simply applies magic regularly.
>> >>
>> >> Marshall
>> >>
>> >> On Thu, Nov 3, 2011 at 11:57 PM, Ricardo 
>> >> Forno<ricardoforno at tutopia.com
>> >wrote:
>> >>
>> >>> I have this verb:
>> >>> magic =: * %>:@(+:@*) - +
>> >>> that I use only as a dyad, and, say,
>> >>> a =: 0.1 * i. 10
>> >>> If I want to get a table of the * verb, I  write:
>> >>> a * / a
>> >>> If I write
>> >>> a magic / a
>> >>> I dont get a table. To get a table, I have to write:
>> >>> a magic"0 / a
>> >>> Why is it so, since both * and magic may be used as dyads?
>> >>> Thanks.
>> >>>
>> >>>
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>
>
>
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