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#!/usr/bin/perl -s
use v5.16;
use Test2::V0;
our ($tests, $examples);
run_tests() if $tests || $examples; # does not return
die <<EOS unless @ARGV;
usage: $0 [-examples] [-tests] [N ...]
-examples
run the examples from the challenge
-tests
run some tests
N ...
swap nibbles in N
EOS
### Input and Output
say swap_nibbles($_) for @ARGV;
### Implementation
# This works portably for N < 2**32 and potentially up to N < 2**64. No
# need to restrict to N < 256.
sub swap_nibbles {
no warnings 'portable';
hex unpack 'h*', pack 'J>', shift;
}
### Examples and tests
sub run_tests {
SKIP: {
skip "examples" unless $examples;
is swap_nibbles(101), 86, 'example 1';
is swap_nibbles(18), 33, 'example 2';
}
SKIP: {
skip "tests" unless $tests;
is swap_nibbles(0), 0, 'all zero';
is swap_nibbles(255), 255, 'all one';
is swap_nibbles(129), 24, 'swap outer bits to inner bits';
is swap_nibbles(0xfedc), 0xefcd, '16 bit';
is swap_nibbles(0xfedcba98), 0xefcdab89, '32 bit';
no warnings 'portable';
is swap_nibbles(0xfedcba9876543210), 0xefcdab8967452301, '64 bit';
}
done_testing;
exit;
}
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