Almost there. first itself is (almost) perfectly respectful of a lazy @_. In List::Util, the pure-perl version of first() is:
sub first (&@) {
my $code = shift;
foreach (@_) {
return $_ if &{$code}();
}
undef;
}
The issue is (almost) completely that @_ is not lazy in the slightest. This is one of the biggest changes no-one will notice in Perl6 - the addition of the concept of truly lazy lists. You could code up something lazier with Tie::Array::Lazy. Maybe something like:
open my $fh, '<', $filename or die "Cannot open '$filename' for readin
+g: $!\n";
tie my @arr, 'Tie::Array::Lazy', [], sub { scalar <$fh> };
first { <whatever> } @arr;
(Note that this is completely untested - I've never used Tie::Array::Lazy in my life.)
My criteria for good software:
- Does it work?
- Can someone else come in, make a change, and be reasonably certain no bugs were introduced?
-
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.
|