Your original code with strict and warnings:
use strict;
use warnings;
sub twice { 2 * $_[0] }
my @a = map twice, 1..3;
print "@a\n";
gives the warning
"Use of uninitialized value $_[0] in multiplication (*) at map1.pl line 3".
This is how it should be written:
use strict;
use warnings;
sub twice { 2 * $_[0] }
my @a = map twice($_), 1..3;
print "@a\n";
which produces 2 4 6 as expected.
BTW, Conway, in
Perl Best Practices, chapter 8,
recommends always using the block
form of map, not the expression form that you are using.
The expression form might be faster than the block form
though
(if that matters, you should benchmark it).
-
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.
|
