Sorry, my wording is incorrect, DOJ said 'confined to 4 elements', the
example 3. which is
a ; a ; a=:10
The copula only needs 3 elements for evaluation, that is rule 7 in that
dictionary page.
The execution of copula inside string is deferred so that J interpreter
does not count them.
Втр, 26 Окт 2010, Ian Clark писал(а):
> Thank you Bill.
>
> I'd only just met the behaviour yesterday, with (;) in place of '([)
> -- which works too, and is slightly more revealing...
>
> I was just playing with Ambrus's example, trying to make it
> conceptually even simpler. I find I can get the effect to work with
> (".) as well as (3 :), which is good. Because coding grunts won't
> relate to themselves defining a verb in-line, but executing a string
> is much more likely.
>
> I'd got to here, and was puzzling about sample 3 vs sample 2, when
> your reminder arrived of how J parses "trains" (have I got the right
> term?) -- in order to implement hooks and forks I guess.
> ____________________
> a=: 5
> a ;; 3 :'a=: 10'0 NB. ;; needed for same reason as [[
> +--+--+
> |10|10|
> +--+--+
>
> a=: 5
> a ; a ; (3 :'a=: 10')0 NB. J needs to read last 4 tokens at once
> +--+-+--+
> |10|5|10|
> +--+-+--+
>
> a=: 5
> a ; a ; (a=:10) NB. but here it doesn't
> +--+--+--+
> |10|10|10|
> +--+--+--+
>
> a=: 5
> a ; a ; ".'a=:10' NB. but here again it does
> +--+-+--+
> |10|5|10|
> +--+-+--+
>
> a=: 5
> a ;; ".'a=:10' NB. so this is safer
> +--+--+
> |10|10|
> +--+--+
> ____________________
>
>
> On Tue, Oct 26, 2010 at 3:42 PM, bill lam <[email protected]> wrote:
> > Thank you, indeed very simple example.
> >
> > Ian, J interpreter have to read the last 4 elements [1] just before
> > evaluation of [
> >
> > a [ v 0 ( noun verb verb noun )
> >
> > so that before the monad v is evaluated, the value of a has already been
> > read into stack. The side effect of v does not change the value of a which
> > is already inside the stack.
> >
> > [1] ~help/dictionary/dicte.htm
> >
> > Втр, 26 Окт 2010, Zsbán Ambrus писал(а):
> >> 2010/10/26 Ian Clark <[email protected]>:
> >> > Can you give a very simple example please, Bill, where [[ would make a
> >> > difference?
> >>
> >> a=: 5
> >> 2*a[3 :'a=: 10'0
> >> 10
> >> a=: 5
> >> 2*a[[3 :'a=: 10'0
> >> 20
> >>
> >> Ambrus
> >> ----------------------------------------------------------------------
> >> For information about J forums see http://www.jsoftware.com/forums.htm
> >
> > --
> > regards,
> > ====================================================
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> > gpg --keyserver subkeys.pgp.net --recv-keys 4434BAB3
> > ----------------------------------------------------------------------
> > 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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