[Jprogramming] i.0 vs i. 0 0

[Pascal Jasmin]

wiki page here... hopefully accurate

http://www.jsoftware.com/jwiki/PascalJasmin/i_dot_0_and_i_dot_0_0?highlight=%28PascalJasmin%2F%29

--- Henry Rich <HenryHRich at nc.rr.com> wrote:

> Here's some information; why don't you start a Wiki
> page?
> 
> 
> i. 0   is   0$0
> 
> i. 0 0    is  0 0 $ 0
> 
> The display of a rank-2 array is each line, with LF
> appended to the end of each line.
> 
> So, for 0 0 $ 0   you get no lines, no LF.
> 
> for 0 $ 0  you get one (empty) line, ended by LF
> 
> 
> +/ applied to an empty list produces an identity
> item: an item made up of identity elements.
> 
> +/ 0 $ 0    the item is a scalar, there are none of
> them,
>   so the result is the identity scalar (shape '')
> 
>    $ +/ i. 0
> 
> 
> +/ 0 0 $ 0   the item is a 0-length list, there are
> none of
>   them, so the result is an identity item: a
> 0-length list
>   (values are 0 but there are no values):
> 
>    $ +/ i. 0 0
> 0
> 
> 
> Henry Rich
> 
> 
> > -----Original Message-----
> > From: programming-bounces at jsoftware.com 
> > [mailto:programming-bounces at jsoftware.com] On
> Behalf Of Pascal Jasmin
> > Sent: Monday, September 25, 2006 12:33 PM
> > To: Programming forum
> > Subject: [Jprogramming] i.0 vs i. 0 0
> > 
> > in the J console,
> > i.0 will return a blank line, while i.0 0 returns
> > nothing, and
> > 
> >    (i.0) -: i. 0 0
> > 0
> >    '' -: i.0
> > 1
> >    (i.0) ; i. 0 0
> > &#9484;&#9516;&#9488;
> > &#9474;&#9474;&#9474;
> > &#9492;&#9524;&#9496;
> >    +/ each (i.0) ; i. 0 0
> > &#9484;&#9472;&#9516;&#9488;
> > &#9474;0&#9474;&#9474;
> > &#9492;&#9472;&#9524;&#9496;
> > I don't really understand the difference between
> the 2
> > values, and am surprised by the last result.
> > I remember a scattering of references to each i.0
> and
> > i. 0 0, and think it should have its own index
> page. 
> > is it as simple as i.0 is empty and i.0 0 is nil?
> > 
> > 
> > Could you help list where each is used inside J,
> and
> > when each version is more helpful (or gets you in
> less trouble?)
> > 
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