Perl

Tags / Perl

This little program uses currying to create a nested function reference that prints out a table with all possible permutations of the @states array in as many columns as you like.

#!/usr/bin/env perl
use strict;
use warnings;
use feature 'say';

## Scott Wiersdorf
## Created: Sat Aug 18 14:29:03 MDT 2012

## permutation/truth table generator

my $inputs = shift @ARGV || 3;  ## table columns
my @states = ('T', 'F', '-');   ## possible states

my $func = sub { say join "\t" => @_ };
for (1..$inputs) {
    $func = loop_maker($func);
}
$func->();

exit;

sub loop_maker {
    my $inner = shift;

    return sub {
        for my $state ( @states ) {
            $inner->(@_, $state);
        }
    };
}

The output with an argument of ‘2’ looks like:

2012-08-24

Perl SSL Debugging

I just spent about 3 hours trying to figure out why a Mojolicious daemon wasn’t permitting SSL connections. Here’s what I checked:

the server was accessible (iptables, routing, etc.)
the port was accessible (I could set mojo’s listen to http://*:443) and it would respond fine on my laptop
the entire /usr/local hierarchy, /etc and /home/scott were identical to my development environment (save the machine specific differences) and had the same permissions and ownership.

So basically at this point I narrowed it down to SSL. Something in the SSL setup wasn’t correct.

2012-07-06

Perl Hash Reference Slices

Working with Perl’s references can sometimes be confusing. This document illustrates several ways to efficiently take a slice of a hash reference.

Here is a hash reference and an array of keys called @order:

my $row = { foo => 'bar',
            baz => 'blech',
            one => 'uno',
            tres => 'three',
            cuatro => 'four or so' };
my @order = qw(one tres cuatro baz foo);

Here is one way to get a list of values in the order of @order:

2012-05-08