[H-GEN] Which is better?

[Mark Suter]

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Folks,

andrae> My number one rule when it comes to code is
andrae> 
andrae> "Help the reader reason about the code".

Here are two functions to calculate a Fibonacci number[1].  Both
will produce the same correct results; however, there are clearly
differences.  I'd use fib1 until it proved a bottleneck.

    sub fib1 {
	my ($i) = @_;

	return 0 if $i == 0;
	return 1 if $i == 1;

	return recursive($i - 1) + recursive($i - 2);
    }

    sub fib2 {
	sub helper {
	    if ($_[0] % 2 == 0) {
		my @m = helper($_[0] / 2);
		return ( $m[0]**2 + $m[1]**2, $m[1] * ($m[0] + $m[2]), $m[1]**2 + $m[2]**2 );
	    } else {
		return (1, 1, 0) if $_[0] == 1;
		my @m = helper($_[0] - 1);
		return ( $m[0] + $m[1], $m[0], $m[1] );
	    }
	}

	return 0 if $_[0] == 0;
	return 1 if $_[0] == 1;
	return (helper($_[0] - 1))[0];
    }

[1] http://en.wikipedia.org/wiki/Fibonacci_number

Yours sincerely,

- -- Mark John Suter  | I know that you  believe  you understand
suter at humbug.org.au | what you think I said, but I am not sure
gpg key id 2C71D63D | you realise that what you  heard  is not
mobile 0411 262 316 | what I meant.        Robert J. McCloskey
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