Re: Explain Fibonacci one-liner ??

This is an unnecessary obfuscation for no apparent reason. The statement albeit short is very obtuse. JavaFan has given a great explanation of how this obscure thing works.

A Perl implementation of a more traditional and MUCH faster approach is below. Perl allows very obscure looking code to be written, but why do it?

#!/usr/bin/perl -w
use strict;

foreach (1..15)
{
   print fibonacci($_), " ";
}
# prints: 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 

sub fibonacci
{
     my $number = shift;

     my $cur_num   = 1;
     my $prev_num  = 1;
     my $sum;
     
     return 1  if ($number == 1 || $number == 2);
   
   # to get Op's output, supress the above by this:  
   # return "" if ($number == 1 || $number == 2);
   # or of course just start the sequence at a different number
     
     $number -= 2;
   
     while ($number--)
     {
         $sum = $cur_num + $prev_num;
         $prev_num = $cur_num;
         $cur_num  = $sum;
     }
   
     return $sum;
}
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Comment on Re: Explain Fibonacci one-liner ?? Download Code

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Re^2: Explain Fibonacci one-liner ?? by JavaFan (Canon) on May 10, 2010 at 18:27 UTC
And even faster again is a solution based on the property: `F(n) = floor((((1+sqrt(5))/2)n) / sqrt(5)) + 0.5)` [download] `my $PHI = (1 + sqrt(5)) / 2; sub fib ($) {int($PHI $_[0] / sqrt(5) + 0.5)} say fib $_ for 0 .. 10; __END__ 0 1 1 2 3 5 8 13 21 34 55` [download]	[reply] [d/l] [select]

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Re^2: Explain Fibonacci one-liner ??
by JavaFan (Canon) on May 10, 2010 at 18:27 UTC

  F(n) = floor((((1+sqrt(5))/2)**n) / sqrt(5)) + 0.5)
[download]

my $PHI = (1 + sqrt(5)) / 2;
sub fib ($) {int($PHI ** $_[0] / sqrt(5) + 0.5)}
say fib $_ for 0 .. 10;
__END__
0
1
1
2
3
5
8
13
21
34
55
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