#!/usr/bin/perl
use strict;
use warnings;
use bignum;

print "Fibonnaci Fun\n\n";

print "Pick a number that represents which value of the Fibonnaci sequence you want to start with\n";
print "ie: 1 would be 1, and 2 would be 1, and 3 would be 2 and so on.\n"; 
print "Your choice: ";
chomp (my $start = <>);

print "\nNow pick a number to repesent the range you want.\n";
print "If you want to use values 1 through 10 you you need only enter 10,\n";
print "assuming of course you entered 1 above.\n";
print "Your choice: ";
chomp(my $range = <>);
print "\n";

for my $fibNum ($start .. $start + $range){
  my $fibValue1 = fib($fibNum);
  my $fibValue2 = fib($fibNum - 1);
  my $phiApprox = $fibNum <= 1 ? '***' : $fibValue1 / $fibValue2;

  print "$fibValue1 / $fibValue2 = $phiApprox\n";
}


my %cache;

sub fib {
    my ($n) = @_;
    return $n if $n < 2;
    
    --$n;
    return ($cache{$n} ||= fib($n)) + ($cache{$n - 1} ||= fib($n - 1));
}