Re: foreach .. stepping?

For syntax, though not efficiency, try:

sub step {
    my $step = shift;
    return grep {($_ - $_[0]) % $step == 0} @_
}

foreach (step 5, 2 .. 100) {
  print "$_ "
}
[download]

which prints:

2 7 12 17 22 27 32 37 42 47 52 57 62 67 72 77 82 87 92 97
[download]

Comment on Re: foreach .. stepping? Select or Download Code

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Re: Re: foreach .. stepping?n by mce (Curate) on Nov 20, 2002 at 13:39 UTC
Hi, But the fastest solution is using a closure: `sub step { my $step=shift; my $count=0; my @array=@_; return sub { $return=$array[$count]; $count+=$step; return $return }; }; for ( my $s=step(5,2..100); my $res=&$s ; 1 ) { print "$res "; }` [download] My benchmark shows 6 times faster than the map, and 10 times faster than the step method. The reason is that I transfer an array only once, and than do queries in the array, whilst with map or step, one iterates over more than one array (map/grep and foreach). --------------------------- Dr. Mark Ceulemans Senior Consultant IT Masters, Belgium	[reply] [d/l]

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Re: Re: foreach .. stepping?n
by mce (Curate) on Nov 20, 2002 at 13:39 UTC

But the fastest solution is using a closure:

sub step {
   my $step=shift;
   my $count=0;
   my @array=@_;
   return sub {
      $return=$array[$count];
      $count+=$step;
      return $return
      };
   };
 
for ( my $s=step(5,2..100); my $res=&$s ; 1 ) {
   print "$res ";
   }
[download]

map

step

The reason is that I transfer an array only once, and than do queries in the array, whilst with map or step, one iterates over more than one array (map/grep and foreach).
---------------------------
Dr. Mark Ceulemans
Senior Consultant
IT Masters, Belgium

[reply]
[d/l]