This is significantly faster than using eval:
sub count
{
my ($string, $char) = @_;
my $index = -1;
my $count = -1;
do {
$count++;
$index = index($string, $char, $index + 1);
} while ($index != -1);
return $count;
}
And this is faster still:
sub count
{
my ($string, $char) = @_;
$string =~ s/[^$char]//g;
return length($string);
}
Eval: 56 wallclock secs (45.19 usr + 0.00 sys = 45.19 CPU) @
+3319.32/s (n=150000)
While Loop: 5 wallclock secs ( 4.69 usr + 0.00 sys = 4.69 CPU) @
+31982.94/s (n=150000)
Substitution: 1 wallclock secs ( 1.41 usr + 0.00 sys = 1.41 CPU) @
+106382.98/s (n=150000)
Update (7/19/00): Oh, duh. s/// returns a count of
the number of changes made. Here's a faster way to write
the subroutine:
sub count
{
my ($string, $char) = @_;
return ($string =~ s/$char//g);
}
- Matt
-
Are you posting in the right place? Check out Where do I post X? to know for sure.
-
Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
<code> <a> <b> <big>
<blockquote> <br /> <dd>
<dl> <dt> <em> <font>
<h1> <h2> <h3> <h4>
<h5> <h6> <hr /> <i>
<li> <nbsp> <ol> <p>
<small> <strike> <strong>
<sub> <sup> <table>
<td> <th> <tr> <tt>
<u> <ul>
-
Snippets of code should be wrapped in
<code> tags not
<pre> tags. In fact, <pre>
tags should generally be avoided. If they must
be used, extreme care should be
taken to ensure that their contents do not
have long lines (<70 chars), in order to prevent
horizontal scrolling (and possible janitor
intervention).
-
Want more info? How to link
or How to display code and escape characters
are good places to start.