Re: Array/list transformations.
On Tue, Dec 27, 2005 at 01:13:10PM -0500, Rob Kinyon wrote: : On 12/27/05, Larry Wall <[EMAIL PROTECTED]> wrote: : > On Tue, Dec 27, 2005 at 12:10:45AM -0500, Rob Kinyon wrote: : > : Creating an array whose positions are aliases for positions in another : > : array can be useful. How about : > : : > : my @s := @a[0,2,4] is alias; : > : : > : @a[2] = 3; # @s[1] == 3 : > : @s[1] = 4; # @a[2] == 4 : > : : > : The default slicing behavior would default to "is copy", to preserve : > : the current semantics. Does that sound reasonable? : > : > Hmm. Assignment is already adequate for copying semantics. And binding : > the individual elements can presumably be done by: : > : > my [EMAIL PROTECTED] := @a[0,2,4]; : : What's the difference between: : : my @s := @a[0,2,4]; : : and : : my [EMAIL PROTECTED] := @a[0,2,4]; : : ? As with function parameter binding, the first would attempt to bind only the first argument, that is, @a[0]. The main difference between := and parameter binding is that := defaults to rw instead of readonly. Larry
Re: Array/list transformations.
On 12/27/05, Larry Wall <[EMAIL PROTECTED]> wrote: > On Tue, Dec 27, 2005 at 12:10:45AM -0500, Rob Kinyon wrote: > : Creating an array whose positions are aliases for positions in another > : array can be useful. How about > : > : my @s := @a[0,2,4] is alias; > : > : @a[2] = 3; # @s[1] == 3 > : @s[1] = 4; # @a[2] == 4 > : > : The default slicing behavior would default to "is copy", to preserve > : the current semantics. Does that sound reasonable? > > Hmm. Assignment is already adequate for copying semantics. And binding > the individual elements can presumably be done by: > > my [EMAIL PROTECTED] := @a[0,2,4]; What's the difference between: my @s := @a[0,2,4]; and my [EMAIL PROTECTED] := @a[0,2,4]; ? Rob
Re: Array/list transformations.
On Tue, Dec 27, 2005 at 12:10:45AM -0500, Rob Kinyon wrote: : Creating an array whose positions are aliases for positions in another : array can be useful. How about : : my @s := @a[0,2,4] is alias; : : @a[2] = 3; # @s[1] == 3 : @s[1] = 4; # @a[2] == 4 : : The default slicing behavior would default to "is copy", to preserve : the current semantics. Does that sound reasonable? Hmm. Assignment is already adequate for copying semantics. And binding the individual elements can presumably be done by: my [EMAIL PROTECTED] := @a[0,2,4]; Larry
Re: Array/list transformations.
On 12/22/05, Jonathan Scott Duff <[EMAIL PROTECTED]> wrote: > On Thu, Dec 22, 2005 at 04:47:21PM +0100, Michele Dondi wrote: > > Also I wonder if one will be able to push(), pop(), etc. array slices as > > well whole arrays. A' la > > > > my @a=qw/aa bb cc dd ee/; > > my $s=pop @a[0..2]; # or [0,2] or just [0] for that matters! > > # $s='cc'; > > # @a=qw/aa bb dd ee/; => same as what I can do with slice() > > > > Not terribly necessary, but indeed consistent IMHO. > > Not quite sure why you'd want this, but if we have something like this: > > my @a = qw/aa bb cc dd ee/; > my @slice := @a[0..2]; > my $s = pop @slice; > > (where @slice is a "reference" to part of @a) > > You get what you want and more. To echo Scott's point, @a[0..2] === @a.splice(0,3). Now, a more interesting problem is @a[0,2,4], which doesn't map to a single splice() call. Ruby's syntax for this is problematic, which points to a problem with how the solutionspaces are mapping to the problemspaces. Creating an array whose positions are aliases for positions in another array can be useful. How about my @s := @a[0,2,4] is alias; @a[2] = 3; # @s[1] == 3 @s[1] = 4; # @a[2] == 4 The default slicing behavior would default to "is copy", to preserve the current semantics. Does that sound reasonable? Rob
Re: Array/list transformations.
On Thu, Dec 22, 2005 at 04:47:21PM +0100, Michele Dondi wrote: > This is not a substantial issue regarding Perl 6, but is more a minor > feature curiosity/meditation. It was inspired some time ago by this PM > node: > > http://perlmonks.org/?node_id=509310 > > I was wondering if in addition to push(), pop() etc. there could be be > rot() and roll() methods that would act upon lists (not modifying them) > like thus: > > (qw/aa bb cc dd ee/).rot(2) # qw/cc dd ee aa bb/ > (qw/aa bb cc dd ee/).rot()# qw/bb cc dd ee aa/ => same as .rot(1) > (qw/aa bb cc dd ee/).roll(2) # qw/dd ee aa bb cc/ => same as .rot(-2) > (qw/aa bb cc dd ee/).roll() # qw/ee aa bb cc dd/ => same as .roll(1) "rot" doesn't conjur the right stuff for me, sorry. Since we already have shifting operators, why not just (re)use them? If +< is "numeric" left shift, maybe @< is "array" left shift. Of course, then you'd have to figure how to vary the wrapping semantics. my @a = qw/aa bb cc dd ee/; @a = @a @< 2; # or @a @<= 2; my @b = @a @> 4; Okay, I'm already not liking that syntax, but the idea is the same: we have "shifting" ops, let capitalize on that meme. > ... > etc. > > Also I wonder if one will be able to push(), pop(), etc. array slices as > well whole arrays. A' la > > my @a=qw/aa bb cc dd ee/; > my $s=pop @a[0..2]; # or [0,2] or just [0] for that matters! > # $s='cc'; > # @a=qw/aa bb dd ee/; => same as what I can do with slice() > > Not terribly necessary, but indeed consistent IMHO. Not quite sure why you'd want this, but if we have something like this: my @a = qw/aa bb cc dd ee/; my @slice := @a[0..2]; my $s = pop @slice; (where @slice is a "reference" to part of @a) You get what you want and more. -Scott -- Jonathan Scott Duff [EMAIL PROTECTED]
Array/list transformations.
This is not a substantial issue regarding Perl 6, but is more a minor feature curiosity/meditation. It was inspired some time ago by this PM node: http://perlmonks.org/?node_id=509310 I was wondering if in addition to push(), pop() etc. there could be be rot() and roll() methods that would act upon lists (not modifying them) like thus: (qw/aa bb cc dd ee/).rot(2) # qw/cc dd ee aa bb/ (qw/aa bb cc dd ee/).rot()# qw/bb cc dd ee aa/ => same as .rot(1) (qw/aa bb cc dd ee/).roll(2) # qw/dd ee aa bb cc/ => same as .rot(-2) (qw/aa bb cc dd ee/).roll() # qw/ee aa bb cc dd/ => same as .roll(1) ... etc. Also I wonder if one will be able to push(), pop(), etc. array slices as well whole arrays. A' la my @a=qw/aa bb cc dd ee/; my $s=pop @a[0..2]; # or [0,2] or just [0] for that matters! # $s='cc'; # @a=qw/aa bb dd ee/; => same as what I can do with slice() Not terribly necessary, but indeed consistent IMHO. Michele -- you'll see that it shouldn't be so. AND, the writting as usuall is fantastic incompetent. To illustrate, i quote: - Xah Lee trolling in clpmisc, "perl bug File::Basename and Perl's nature"
