Re: run-once code
On Tue, 13 Jan 2004 20:37:21 -0800
David Storrs <[EMAIL PROTECTED]> wrote:
> Given this code:
>
> if ( some_expensive_lookup_function() >= $MAX_RECORDS ) {
>mark_that_we_have_reached_max_records();
>return;
> }
>
> After I enter that block once, I never want to evaluate the condition
> again--I want the code to completely disappear from the bytecode (or,
> at least, be jumped around). How would I do that in Perl 6?
Another approach would be to just memoize the subroutine. Thanks to the
spiffy new subroutine signature syntax it's absurdly easy e.g
sub some_expensive_lookup_function() is cached { ... }
That's side-stepping the implications of memoizing a subroutine of
course, but it does save maintaining state in user-level code.
Dan
Re: Aliasing an array slice
On 5 Jul 2003, Luke Palmer wrote:
> > return [EMAIL PROTECTED] $begin .. $end ];
>
> I fear that this might take a reference to each element in the slice,
> rather than a reference to the slice
Yes, that would indeed return a list of refs in perl5. Can it also be
assumed that the magic hyper-operation of \() in perl5 will translated to
perl6, or (hopefully) will this behaviour become more explicit with
something like ^\() (is the carat still the hyper-operator character
btw?) ?
> Actually, you can't reference a slice! Where the heck does the
> reference point?
Maybe this is a poor simile since references aren't pointers, but I would
imagine if references to slices were to exist they'd be something *like*
a pointer to a specific index in an array in C e.g
#include
int main(void) {
char *str = "a list of characters";
char *p = &str[2];
puts(p);
return 0;
}
__output__
list of characters
Of course this isn't directly orthogonal to a reference of an array slice
but hopefully it illustrates my point. Or perhaps this could all just be
simply implemented with a tie() or some other such magic. Just thinking
out loud here :)
Dan Brook
Aliasing an array slice
Will it be possible (or sane even) to bind a variable to an array slice e.g ## correct syntax? my @array = << a list of values >>; my @array_slice := @array[ 1 .. @array.end ]; Or would this merely bind @array_slice to the list returned by the slice, or would it DTRT (in my eyes at least) and bind it to that particular slice of @array? Dan Brook
Re: "Disappearing" code
On Thu, 09 Jan 2003 19:55:20 -0500 John Siracusa <[EMAIL PROTECTED]> wrote: > Has there been any discussion of how to create code in Perl 6 that's > there under some conditions, but not there under others? I'm thinking > of the spiritual equivalent of #ifdef, only Perlish. If the perl6 command-line options are anything like perl5 then you can just use the -P switch if preprocessor commands are your thing. > In Perl 5, there were many attempts to use such a feature for > debugging and assertions. There has also been a proposal for patching perl5 to add assertions which was recently discussed[1] on p5p, which if accepted has implications for assertions in perl6 surely. Dan [1] http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2002-11/msg00325.html
