[Jprogramming] Re: How to do that in J?

[Henry Rich]

My memory is that amend is not in-place on boxed
arrays, but I can't find confirmation of that in the Dictionary.
Can anyone?

Henry Rich 

> -----Original Message-----
> From: programming-bounces at jsoftware.com 
> [mailto:programming-bounces at jsoftware.com] On Behalf Of Mark 
> D. Niemiec
> Sent: Tuesday, April 18, 2006 9:29 PM
> To: programming at jsoftware.com
> Subject: [Jprogramming] Re: How to do that in J?
> 
> "Miller, Raul D" <rdmiller at usatoday.com> wrote:
> Re: How to do that in J?
> > Mark D. Niemiec wrote:
> > >  memory =: register address } memory
> > > do not actually copy the entire memory array
> >
> > Perhaps.
> >
> > I'm seeing well over an order of magnitude
> > difference in timing for operations matching 
> > the above pattern.  I don't really know what
> > is going on.
> 
> A few things can force a copy.
> For one, if the pattern is not recognized as
>   y =: x m } y
> (or =.)
> In particular, while x and m can be sophisticated
> expressions, both occurrances of y must be unadorned.
> 
> Another is if a type conversion is required,
> such as amending an integer array with a real
> value.
> 
> A third could happen if the two y's here are
> in different scopes (this can happen with =.
> if a global y exists but a local one does not
> exist yet - the first such amend ought to
> create a local copy).
> 
> -- Mark D. Niemiec <mniemiec at interserv.com>
> 
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