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#!/Users/colincrain/perl5/perlbrew/perls/perl-5.32.0/bin/perl
#
# nibble-n-swap.pl
#
# Swap Nibbles
# Submitted by: Mohammad S Anwar
# You are given a positive integer $N.
#
# Write a script to swap the two nibbles of the binary representation of
# the given number and print the decimal number of the new binary
# representation.
#
# A nibble is a four-bit aggregation, or half an octet.
#
# To keep the task simple, we only allow integer less than or equal to
# 255.
#
# Example
# Input: $N = 101
# Output: 86
#
# Binary representation of decimal 101 is 1100101 or as 2 nibbles (0110)(0101).
# The swapped nibbles would be (0101)(0110) same as decimal 86.
#
# Input: $N = 18
# Output: 33
#
# Binary representation of decimal 18 is 10010 or as 2 nibbles (0001)(0010).
# The swapped nibbles would be (0010)(0001) same as decimal 33.
#
#
# © 2021 colin crain
## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ##
use 5.32.0;
use warnings;
use strict;
use utf8;
use feature qw(signatures);
no warnings 'experimental::signatures';
my $num = shift @ARGV // 3;
0 < $num < 256 or die "number must be in range 1 to 255 inclusive";
my $bin = sprintf "%08b", $num;
substr( $bin, 0, 4 ) = substr( $bin, 4, 4, substr( $bin, 0, 4));
say oct "0b$bin";
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