sub is_fibonnacci {
    my $plus = (5 * $_[0] * $_[0]) + 4;
    my $mins = (5 * $_[0] * $_[0]) - 4;
    return is_perfect_square($plus) | is_perfect_square($mins);
}
[download]

No need to calculate 5 * $_[0] * $_[0] twice, and you probably meant to use the logical or operator instead of the bit-wise or operator.

sub is_fibonnacci {
    my $plus = (5 * $_[0] * $_[0]) + 4;
    my $mins = $plus - 8;
    return is_perfect_square($plus) || is_perfect_square($mins);
}
[download]

(The logical operators short-circuit so is_perfect_square($mins) will only execute if is_perfect_square($plus) is true.)

sub is_perfect_square {
    my $sqrt = int(sqrt($_[0]));
    return $sqrt * $sqrt == $_[0];
}
[download]

Or just:

sub is_perfect_square { int( $_[0] ** .5 ) ** 2 == $_[0] }
[download]

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.