Re: Reduce [was: Re: Random items (old p5p issues)]

[John Porter]

Graham Barr wrote:
> > > But then went onto interators and something like
> > > 
> > >   @list = interleave(@a,@b,@c);
> > > 
> > > which would interleave the lists given, and
> > > 
> > >   foreach ($a,$b,$c) (interleave(@a,@b,@c))

  sub interleave(\@;\@\@\@\@\@\@\@\@) {
    my $m = -1;
    for ( @_ ) { $m < $#{$_} and $m = $#{$_} }
    map { my $i = $_; [ map { $_->[$i] } @_ ] } 0..$m;
  }

  for ( map { @$_ } interleave( @a, @b, @c ) )


> Gisle Aas wrote:
> > Python also has a map function that can take multiple lists and iterate
> > over them in sync.  E.g.
> > 
> >   map(func, list1, list2, list3)
> > 
> > where 'func' must be a function taking 3 arguments.  Can't see how to
> > easily extend perl's map in that way.  Perhaps we could introduce
> > map2, map3,... builtins? :-)

sub mapf(&;\@\@\@\@\@\@\@\@\@) {
  my $cr = shift;
  my $m = -1;
  for ( @_ ) { $m < $#{$_} and $m = $#{$_} }
  map { my $i = $_; $cr->( map { $_->[$i] } @_ ) } 0..$m;
}


I guess my question is, why do these need to be builtins?

There is no limit to the funky algorithms one can come up with;
not everyting should go in the core.


-- 
John Porter

        Aus tiefem Traum bin ich erwacht.