The clocks go back this weekend and the deadline of Friday 27th October for your LPW talk submissions is fast approaching!

As you’ve probably seen from earlier posts, we already have some fantastic speakers and subjects lined up, but there’s room for a few more, so if you have an idea you’ve been musing on, now is the time to tell us about it at londonperlworkshop.org/newtalk

Done is Better Than Perfect. Your proposal doesn’t have to be polished - we are happy to provide guidance and suggestions even if it’s just an idea or an outline. Think MVP (that’s Minimum Viable Proposal ;-), get it in ahead of the weekend and we will help you refine it.

We are looking forward to seeing as many of us as possible sharing our experiences and contributing to our community on Saturday 25th November 2017.

Its two steps backward day here in the Moose-Pen

I left off yesterday by fixing a bug on the Gather class that allowed you to create a Gather with an empty set of 'elements' like this;

gather => {
        elements => [],
        conditions=>[{
                left => {
                    name => 'last_name',
                },
                right             => { value => 'Bloggings' },
                operator          => '=',
            },]
            },

I was fortunate to be invited to participate in the 2017 Perl 5 Core Hackathon (P5H) held in Amsterdam from Thursday, October 12 to Sunday, October 15. This event brings together contributors to the Perl 5 core development process -- often referred to as the "Perl 5 Porters" (P5P) -- for discussion on the current state and future of the language and for hacking to get us to that future state.

Version 0.16 of GraphQL implements most of using the Schema Definition Language to create schemas, rather than doing so programmatically. So let's now translate all the idioms in the JavaScript GraphQL tutorial into Perl!

EDIT version 0.17 implements the rest, so this tutorial translated has been updated slightly as you don't need to specify a schema at all if you call your query type Query, etc.

The format I'll use is to give each of the JS tutorial pages, with the Perl code to do what's given there:

Getting Started With GraphQL.js

You will need Perl 5.14. Consider using perlbrew to get this.

cpanm Mojolicious::Plugin::GraphQL # also gets Mojolicious and GraphQL

Then the first script:

At the Toolchain Summit this year, one of the discussion sessions was to reflect on how the DBIx::Class ownership conflict was handled. We didn't only discuss DBIx::Class, but how a range of other situations were handled. One of the outcomes of that session was a request that the PAUSE admins document the rules and principles for how PAUSE is operated, and how various situations are, or will be going forward, resolved.

Since then the PAUSE admins have been discussing various scenarios and gradually working on a document which we ended up calling the PAUSE Operating Model. The name reflects that it not only describes how PAUSE works, but how the PAUSE admins run the service.

The rest of this post gives an outline of what the document covers, and where you can read it.

Its a good day for code but a bad one for posts here in the Moose-Pen

I started off today by adding in some 38 new tests to 40_joins.t in Driver::DBI and after one or two runs to get rid of some typos in my expected results they are all passing. So like the title says a good day for code but a bad one for posts as I have nothing to much to report on.

Undaunted I moved into 50_having.t and the first thing I did was rename it to 50_group_by.t as that is a little more SQLish.

After coming up with some 34 new tests and after a few runs to get rid of my usual typos in my expected SQL I still got two errors on the generated SQLthat where far from obvious.

In both cases

Many of you who have been around computers for as long as I have remember the Semantic Web. It was touted in the late 1990’s and early 2000’s as a way to organise and reason over the Web. This was before the rise of Google and the modern web as we know it today. Mostly, the Semantic Web died because of the problem with Metacrap. However, the idea was resurrected in 2006 as Linked Data. The problem has since been relegated to academia, a few Government projects, like UK’s data.gov.uk, and, interestingly, bio-medical.

AppVeyor is a continuous integration service similar to Travis CI, just on Windows. If you have a Perl module on GitHub, it's not that hard to have it run tests automatically on Windows; it's just not well documented.

(The following information was taken from https://blogs.perl.org/users/eserte/2016/04/testing-with-appveyor.html, the AppVeyor documentation, and random trial and error.)

First you need to sign in to AppVeyor with your GitHub account and let it access your repositories, as described on https://www.appveyor.com/docs/.

Then you need to add a .appveyor.yml file to your repository. Mine looks like this:

According to this test my module JSON::Parse wasn't working on Cygwin. I have a Windows computer with Cygwin installed, so I thought I would try to compile the module myself. The first problem I encountered was that the cpan shell command didn't work. It would print odd-looking errors and hang up at the following prompt:

What approach do you want?  (Choose 'local::lib', 'sudo' or 'manual')

So I decided to download the module myself with wget and compile it. The next problem was that I hadn't got wget in my cygwin, so I had to install that. After downloading and untarring the file, I tried the usual

perl Makefile.PL

then "make", and got a rather baffling error

fatal error: EXTERN.h: No such file or directory

So it is little progress day here in the Moose-Pen

Carrying on from yesterday's post I decided to get 57_dad_elements in order so I added in a few more tests;

The Lab::Measurement project provides Open Source control of Test & Measurement devices with Perl. This post introduces the new Test & Measurement back end modules Lab::VXI11 and USB::TMC. Both VXI-11 and USBTMC are open standards and are supported by most modern T & M devices. They were developed as alternatives to the legacy GPIB (General Purpose Interface Bus). The main purpose of GPIB is to transfer text messages between the measurement PC and an automated measurement device, such as a digital multimeter. Beyond that, it defines various control commands for device triggering, setting end-of-message characters, reading a status byte and much more. VXI-11 and USBTMC provide a high degree of backwards compatibility with these features.

The photo shows the rear panel of an Agilent 34410A digital multimeter. While it is a small and (relatively) cheap device, it supports four different automation standards (GPIB, USBTMC, VXI-11, raw TCP sockets). This is why I used it for most of my testing.

In Perl 5, until is a negated version of while. Instead of writing this:

while (defined(my $i = $iter->next())) {
    say $i;
}

Using until allows you to write this:

until (!defined(my $i = $iter->next())) {
    say $i;
}

until is documented under the "Compound Statements" heading of the perlsyn document.

Practice and policy

The thoroughly excellent book Perl Best Practices by Damian Conway (DCONWAY), the Black Wizard of Perl, exhorts us not to use the until control structure at all. The core policy set from the similarly excellent Perl::Critic dutifully implements the book's recommendation by raising low-severity warnings if you use it as a block:

A time series database is a massively useful tool for system reporting and monitoring. By storing series of simple values attached to timestamps, an ops team can see how fast their application is processing data, how much traffic they're serving, and how many resources they're consuming. From this data they can determine how well their application is working, track down issues in the system, and plan for future resource needs.

There have been a lot of new databases and tools developed to create, store, and consume time series data, and existing databases are being enhanced to better support time series data.

With the new release of ETL::Yertl, we can easily translate SQL database queries into metrics for monitoring and reporting. I've been using these new features to monitor the CPAN Testers application.

Its get on with it day here in the Moose-Pen

After putting on my thinking Moose-cap and reading though some of my notes (and looking at a number of my older posts) the best solution I could come up with was to leave the ability to add a 'JOIN' to an 'UPDATE', 'CREATE' or 'DELETE' statement in.

My reason for this simple if someone wants to use a JOIN is something other than a 'SELECT' and it is perfectly valid command why should my application stop them.

The original DataAccessor code it is written in such a way that you can only do a JOIN on a SELECT as the concept was to have a class that was for 'CUD' actions and one for 'Retrieve'. I would still like something like that and the way I can establish this is with this attribute;

Dancer2 0.205002 has just been released and is on its way to your favorite CPAN mirror. Highlights include a number of documentation improvements (thank you, simbabque and ambs!) and the fixing of some lingering and pesky bugs (thanks to Nick Tonkin, Pierre Vigier, and our very own bigpresh, ambs, and veryrusty).

The full changelog is as follows:

As a vim user, I've used Syntastic for a long time. It's a great tool for syntax checking. However, I was recently introduced to Ale . Ale does a lot of what Syntastic does, but it does it asynchronously. The practical benefits are

• You should experience less lag when editing large files
• Ale flags problematic lines containing errors and warnings in a gutter, making it easy to find problems
• Detailed information about errors and warnings appear at the bottom of your buffer

I may actually be underselling it. Ale is almost a drop-in replacement for Syntastic. (At least it was for me). Try it out. I don't think you'll go back to Syntastic once you've tried Ale.

I'd like to point out a few configuration tweaks...

Read the full post at http://www.olafalders.com/2017/10/17/vim-ale-syntastic-and-perlcritic/

Summary

This is a library to allow users to write Bitcoin applications, including SPV nodes, in Perl. The library relies on a C library called picocoin . In order to get the library to work with Perl XS, some of the header files were modified and are located here . This set of Perl modules, the customized picocoin library, and all related dependencies have been compiled into debian packages.

This guide goes over setting up a simple HD Tree, drafting a P2SH transaction, and running an SPV client.

For instructions on how to install libcbitcoin-perl, see this page.

As for the Github page for libcbitcoin-perl, look here.

HD Trees

There are several ways to think about an HD Tree. Probably the simplest way is as a "Wallet".

Background

The Perl module CBitcoin::CBHD acts as an intuitive interface in handling BIP32 objects as described below:

It test postette day here in the Moose-Pen.

Today I was rerunning all my test cases to seen which ones where breaking and I got though all of the test on Database::Accessor and was most of the way though Driver::DBI and then I got stuck on '40_joins.t' with this error;

# Expected SQL--> SELECT people.first_name,
people.last_name, people.id, address.street FROM people LEFT JOIN address ON
people.id = address.user_id WHERE people.first_name = ?

# Generated SQL-> SELECT people.first_name, people.last_name, people.id,
address.street FROM people WHERE people.first_name = ?

Hmm, missing the complete JOIN clause there. Now I do not think I made such a basic error as forgetting to call the '_join_clause' sub in the Driver::DBI so the first place I looked was my test and fortunately the test hash was just a little out of date.

Now with the new test hash;

This came into my Inbox just now and looked too good to keep to myself ...

Barcelona Perl & Friends: Saturday 4 Nov 2017

friends.barcelona.pm/2017

A free one-day conference for Geeks and Friends

The computer industry is becoming a place where you are trapped in the feeling that you're missing out if you're not using last week's "hot thing" commented on Twitter, and that no one will be interested if you're not talking about the last functional programming lanaguage, new framework, etc.

The fact is that innovations and amazing things are going on in lots of our "out of sight" communities. Come to show us what you've done, how you like to work, what is working for you and what is not, without the feeling that you'll be frowned upon because you say jQuery, SQL Server, Ruby or Windows.

We're the Perl Community. We want to share with you our ideas and innovations, and want to see yours, no matter what technology you use, what gender you are or where you're from.

As you'd hope, the London Perl Workshop on Nov 25th will feature lots and lots and lots of Perl. But there's also a chance to escape the echo chamber!

• Former leader of the London Perl Mongers Sue Spence will dive into "Spiders, Gophers & Butterflies", looking at how a concurrent web crawler compares written in Go and in Perl 6
• Colin Newell tells us "Why learning a bit of Crypto is good for you", and looks at common security mistakes made by developers who don't know a basic smattering of crypto.
• Steven Goodwin show us (tongue in cheek) paradigms from the 16 languages he's worked with professionally which Perl developers may not be familiar with in "Ada 99 - Rewriting the very first computer program".

As a bonus, Dave Cross will be showing us exactly how the echo chamber is escaped in his lightning talk of the same name!

Attendance is free, so if you can get to London on the 25th of November, register online now at: http://londonperlworkshop.org