I tend to like the mathematical solutions instead.

The following would let you reverse any N elements at a time in an array.

my @foo = (1..15);
my $n = 5;

my @bar = @foo[map {$_ + $n - 1 - 2 * ($_ % $n)} (0..$#foo)];

print "@bar";

[download]

Outputs

5 4 3 2 1 10 9 8 7 6 15 14 13 12 11

[download]

Obviously not as spiffy as using xor to switch odds and evens, but still pretty concise.

Alternatively, if you want to do a rotation of the elements instead of a reversal, you can use the following translation:

my @foo = (1..15);
my $n = 5;
my $i = 2;

my @bar = @foo[map {my $r = $_ % $n; $_ - $r + (($r + $i) % $n)} (0..$
+#foo)];

print "@bar";

[download]

Outputs

3 4 5 1 2 8 9 10 6 7 13 14 15 11 12

[download]

- Miller

In reply to Re^4: Switch the odd/even elements of an array by wind
in thread Switch the odd/even elements of an array by jaredor

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