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#!/usr/bin/env perl
# Author: Steven Wilson
# Date: 2019-06-17
# Week: 013
# Challenge: #2
#
# Write a script to demonstrate Mutually Recursive methods. Two methods
# are mutually recursive if the first method calls the second and the
# second calls first in turn. Using the mutually recursive methods,
# generate Hofstadter Female and Male sequences.
#
# F ( 0 ) = 1 ; M ( 0 ) = 0
# F ( n ) = n − M ( F ( n − 1 ) ) , n > 0
# M ( n ) = n − F ( M ( n − 1 ) ) , n > 0.
use strict;
use warnings;
my $n = 20;
print "female sequence: ";
for ( 0 .. $n ) {
print &f($_) . ", ";
}
print "...\n";
print " male sequence: ";
for ( 0 .. $n ) {
print &m($_) . ", ";
}
print "...\n";
sub f {
my $n = shift;
if ( $n == 0 ) {
return 1;
}
elsif ( $n > 0 ) {
return ( $n - &m( &f( $n - 1 ) ) );
}
}
sub m {
my $n = shift;
if ( $n == 0 ) {
return 0;
}
elsif ( $n > 0 ) {
return ( $n - &f( &m( $n - 1 ) ) );
}
}
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