perlmeditation
Juerd
<p>
In Python, a programming language that I don't like much, you don't use curly braces or keywords to delimit code blocks. Instead, indenting is required. The block ends when indenting ends.
</p>
<p>
I hate forced indenting. Even though I always indent, I don't want this to be necessary - I want to code in my own style, and be able to change that style when I feel like doing so. This is the number one reason for me to not learn anything about Python.
</p>
<p>
But apparently some people like forced indentation and some even use Python because of only that. Well, Perl can do this too. Let's start with an example script, that I will call <tt>test.pl</tt>:
<readmore>
<code>
#!/usr/bin/perl -w
use strict;
$a = 0;
while ($a < 5) {
print ++$a, "\n";
for $b (1..10) {
print "$a $b\n";
}
for $b (11, 12) {
print "$a $b\n";
}
}
print "done\n";
</code>
<small>(Yes, this does use package globals, yes, strict is kind of useless because of that. I just typed "use strict;" because it's a habit. A good one, IMO.)</small>
</readmore>
</p>
<p>
Now let's remove the curlies, since when I'm done, they will be inserted automatically.
<readmore>
<code>
#!/usr/bin/perl -w
use lib ".";
use Test;
use strict;
$a = 0;
while ($a < 5)
print ++$a, "\n";
for $b (1..10)
print "$a $b\n";
for $b (11, 12)
print "$a $b\n";
print "done\n";
</code>
As you can see, I added <tt>use Test;</tt>, because my test module will be named <tt>Test.pm</tt>. I like keeping things simple and obvious. <tt>use lib ".";</tt> is there to make sure I'm not using the other module called [cpan://Test] :).
</readmore>
</p>
<p>
I have no idea how Python's indenting rules are, and don't really want to know either. So I decided to create some rules:
<ul>
<li> A literal tab character has a width of 8
<li> To create a block, increase indent
<li> To end a block, decrease indent, but no more than the indentation of the line before the block that you're ending
</ul>
<readmore>
<code>
foo
bar;
baz
quux
xyzzy
blah;
moo
</code>
equals, more or less:
<code>
foo {
bar;
}
baz;
{
quux {
xyzzy {
blah;
}
}
}
moo
</code>
</p>
<p>
Source filtering is cool. Dangerous and scary, but extremely cool. And with [cpan://Filter::Simple], it's also very easy.
<code>
package Test;
use strict;
use Filter::Simple;
FILTER_ONLY code => sub {
no warnings;
my @lines = split /\n/, $_;
my @indents;
for (@lines) {
my ($indent) = /^(\s*)/;
$indent =~ s/\t/12345678/g;
$indent = length $indent;
if ($indent > $indents[-1]) {
s/^/{/;
push @indents, $indent;
} elsif ($indent < $indents[-1]) {
while ($indent < $indents[-1]) {
defined pop @indents or last;
s/^/}/;
}
}
}
$_ = join "\n", @lines;
$_ .= "}" x @indents;
};
1;
</code>
As this is a quick hack, I added <code>no warnings;</code> to get rid of warnings caused by the initial emptiness of <code>@indents</code>. I also did not do much testing. To be honest: <tt>test.pl</tt> was the only test I did. I hate forced indenting, so I'd rather not write more testing code for this :)
</p>
<p>
Anyway, this works. Maybe Python coders like Perl better now. Perhaps not.
</readmore>
</p>
<p>
Perl can, without a lot of code, support forced indenting. I wonder if Python people can hack up something to support curly delimited blocks in Python, without mandatory indenting.
</p>
<p>
Is Python flexible enough? (I'm asking this in the wrong place; I should be trolling a Python forum instead.)
</p>
<p>
<small>Please do not use this module. Mandatory indenting is evil.</small>
</p>
<p><font color="#800000">
Juerd
# { site => '<a href="http://juerd.nl/" target="_blank"><font color="#800000">juerd.nl</font></a>', plp_site => '<a href="http://plp.juerd.nl/" target="_blank"><font color="#800000">plp.juerd.nl</font></a>', do_not_use => '<a href="mailto:spamcollector_perlmonks@juerd.nl" target="_blank"><font color="#800000">spamtrap</font></a>' }
</font></p>
P.S. / Update: I'm not actually being serious :)<br><br>
Another update:<br>
<pre>
10:09 < scrottie> hrm. should write a source filter that reads white-space structured
perl and adds the { and }'s
10:09 <@Juerd> scrottie: Sorry.
10:09 <@Juerd> scrottie: http://perlmonks.org/index.pl?node_id=266609
10:09 <@Juerd> I win :)
10:09 < scrottie> no kidding!?
10:09 <@Juerd> This was 2 days ago, even :)
10:09 < scrottie> you're a crazy fuck, you know that?
</pre>