When you do things with a mix of javascript/HTML/browser and J you will see
that J may finish more or less immediately and then you may have to wait
quite some time for the others to display and present the results.
The display part can be considerable.
2011/12/22 David Vaughan <purpleblue...@googlemail.com>
> Why should there be any speed up just from assigning the phrase to a noun?
> Surely in both cases the same code has to be executed, one will display the
> result, one will store the result?
>
> ___________________________
>
> David Vaughan
>
> On 22 Dec 2011, at 17:46, Raul Miller <rauldmil...@gmail.com> wrote:
>
> > Actually, I think he was asking why the speedup is not available without
> the =:
> >
> > And I think that has to do with "ease of implementation".
> >
> > Also, if there's no =: then that syntax is almost certainly being used
> > to generate a noun -- it's not being used to build a repeatable
> > operation. You'd have to use different syntax to generate a useful
> > verb.
> >
> > --
> > Raul
> >
> > On Thu, Dec 22, 2011 at 12:24 PM, Devon McCormick <devon...@gmail.com>
> wrote:
> >> In a word: performance.
> >>
> >> a=. 1e6?@$0
> >> b=. <:+:1e6?@$0
> >> c=. 1e6?@$2
> >>
> >> 10 ts 'r=. c}b,:a'
> >> 0.0066557413 8390912
> >> 10 ts 'c}b,:a'
> >> 0.021307987 41945088
> >>
> >>
> >> On Thu, Dec 22, 2011 at 11:00 AM, Johann Hibschman <
> jhibsch...@gmail.com>wrote:
> >>
> >>> Thanks, everyone. I never understood item-amend until now. That's
> >>> exactly what I was looking for. For context, I was reading through the
> >>> APL book and hit the "/a,u,b/" notation, and wondered how to do that
> >>> in J.
> >>>
> >>> One question though: why is the particular form (result=:c}b,:a)
> >>> singled out, rather than the general (c}b,:a)?
> >>>
> >>> On Wed, Dec 21, 2011 at 10:54 AM, Henry Rich <henryhr...@nc.rr.com>
> wrote:
> >>>> Note that
> >>>>
> >>>> c}b,:a
> >>>>
> >>>> does indeed compute b,:a. But if it's used in the precise form
> >>>>
> >>>> result =: c}b,:a
> >>>>
> >>>> the computation is avoided.
> >>>>
> >>>> b =: 1e6$4
> >>>> a =: 1e6$4
> >>>> c=: ? 1e6$ 2
> >>>> ts 'c}b,:a'
> >>>> 0.0401299 2.09725e7
> >>>> ts 'q =: c}b,:a'
> >>>> 0.0112949 4.19558e6
> >>>>
> >>>> There are other special cases; see the Special Code page.
> >>>>
> >>>> Henry Rich
> >>>>
> >>>> On 12/21/2011 11:43 AM, Marshall Lochbaum wrote:
> >>>>> A more obvious way is to use (c { b,.a) . The key is to realize that
> >>> saying
> >>>>> (if c then a else b) is just selection: if c is 0, we pick b, and if
> c
> >>> is
> >>>>> 1, we pick a. So we rephrase as (c { b,a), and J's implicit rank
> allows
> >>> us
> >>>>> to do (c { b,.a) for vector c, a, and b.
> >>>>>
> >>>>> That said, (c} b,:a) is faster, and uses less memory by not actually
> >>>>> computing b,:a . So it's a better choice.
> >>>>>
> >>>>> Marshall
> >>>>>
> >>>>> On Wed, Dec 21, 2011 at 10:26 AM, Brian Schott<
> schott.br...@gmail.com
> >>>> wrote:
> >>>>>
> >>>>>> One way is the following.
> >>>>>>
> >>>>>> c}b,:a
> >>>>>> 10 2 30
> >>>>>>
> >>>>>>
> >>>>>> --
> >>>>>> (B=)
> >>>>>>
> ----------------------------------------------------------------------
> >>>>>> 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
> >>> ----------------------------------------------------------------------
> >>> For information about J forums see http://www.jsoftware.com/forums.htm
> >>>
> >>
> >>
> >>
> >> --
> >> Devon McCormick, CFA
> >> ^me^ at acm.
> >> org is my
> >> preferred e-mail
> >> ----------------------------------------------------------------------
> >> 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
>
--
Björn Helgason, Verkfræðingur
Fornustekkum II
781 Hornafirði,
t-póst: gos...@gmail.com
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twitter: @flugfiskur
http://groups.google.com/group/J-Programming
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