To be clearer, I see more of a problem with > than with }. or {: here.
I understand the reasons for:
> 2; < 2 4 $ i.8
2 0 0 0
0 0 0 0
0 1 2 3
4 5 6 7
$ > 2; < 2 4 $ i.8
2 2 4
$ {: > 2; < 2 4 $ i.8
2 4
$ }. > 2; < 2 4 $ i.8
1 2 4
I guess that I should completely understand why $2 is not 0 or 1, but I can let
my pretty little head just consider that a list of 1 and a scalar must be
different:
$ <2
$ 2
# $ 2
0
$ 2 1
2
$ ,<2
1
$ (i.0),<2
1
$ >,<2
1
I guess that if I can understand the above, I should also understand:
{. > (i.0),<2
2
{. >}. (i.0),<2
┌┐
││
└┘
A very good reason for that behaviour is that code that scans a list, should
expect list items throughout. But there is code such as { {. / that already
work identically on scalars and 1 element lists.
A naive question is should > also have that capability. To answer myself, I
can see the reason not to. List items can be avoided whenever list items are
possible, so the programmer should avoid them when not necessary. Still there
can be gotchas.
;/ (i.0),<2
┌─┐
│2│
└─┘
; (i.0),<2
2
$ ; (i.0),<2
1
----- Original Message -----
From: Ric Sherlock <[email protected]>
To: Programming JForum <[email protected]>
Cc:
Sent: Wednesday, October 2, 2013 7:08:28 AM
Subject: Re: [Jprogramming] strange difference between }. and {:
I think of the distinction as follows:
}. drops the first item from a list. The result is the rest of the list,
however many items that may be.
{: takes the last item from a list. The result is a single item, not a list.
Seems logical to me.
On Wed, Oct 2, 2013 at 5:17 PM, Pascal Jasmin <[email protected]>wrote:
> I am taking the shape after I have opened the item. I'd expect it (the
> insides) to be the same whether I got the item from }. or {:
>
>
>
> ----- Original Message -----
> From: Roger Hui <[email protected]>
> To: Programming forum <[email protected]>
> Cc:
> Sent: Wednesday, October 2, 2013 12:00:27 AM
> Subject: Re: [Jprogramming] strange difference between }. and {:
>
> Not so strange. }. and {: are not equivalent, even on 2-element lists.
>
>
> On Tue, Oct 1, 2013 at 8:56 PM, Pascal Jasmin <[email protected]
> >wrote:
>
> > $ >@}. 2; < 2 4 $ i.8
> > 1 2 4
> > $ >@{: 2; < 2 4 $ i.8
> > 2 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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