For Russian speaking posted translated version here.

This is how Alex Viscreanu’s talk on Moscow Python Conf++ named. Now it's two weeks till before the conference, but of course, I've already heard what Alex will speak about. Find below some spoilers and talk preparing backstage: what kind of an open source Zoo developed in Kiwi, how it tests Python code and what’s the difference between The Zoo and for example mypy.

— Tell us a bit about Kiwi, yourself and what is your work within a company?

Kiwi.com is an online travel agency based in Czech Republic. We aim to make travelling as simple and accessible as possible. The company was founded in 2012 as Skypicker, and since then it has become one of the five biggest online sellers of airline tickets in Europe. It was renamed to Kiwi.com in 2016.

The special feature that we, at Kiwi.com, offer is the virtual interlining, which allows us to connect flights from companies that don’t usually cooperate together, and we are covering the possible connection issues caused by delayed flights.

Some of the numbers that we manage at Kiwi.com include 90 000 000+ daily searches, 25 000 seats sold daily, and a total of 15 000 000 000+ flight combinations available.

Here we are, continuing to explore the code of calculators! Today we are going to take a look at the project called SpeedCrunch, the second most popular free calculator.

Introduction

SpeedCrunch is a high-precision scientific calculator featuring a fast, keyboard-driven user interface. It is free and open-source software, licensed under the GPL and running on Windows, Linux, and macOS.

The source code is available on BitBucket. I was somewhat disappointed by the build documentation, which could be more detailed. It says that you need «Qt 5.2 or later» to build the project, but it actually required a few specific packages, which wasn't easy to figure out from the CMake log. By the way, it is considered a good practice nowadays to include a Dockerfile into the project to make it easier for the user to set up the development environment.

Starting from .NET Core 2.0 and .NET Framework 4.5 we can use new data types: Span and Memory. To use them, you just need to install the System.Memory nuget package:

PM> Install-Package System.Memory

These data types are notable because the CLR team has done a great job to implement their special support inside the code of .NET Core 2.1+ JIT compiler by embedding these data types right into the core. What kind of data types are these and why are they worth a whole chapter?

If we talk about problems that made these types appear, I should name three of them. The first one is unmanaged code.

Both the language and the platform have existed for many years along with means to work with unmanaged code. So, why release another API to work with unmanaged code if the former basically existed for many years? To answer this question, we should understand what we lacked before.

This chapter was translated from Russian jointly by author and by professional translators. You can help us with translation from Russian or English into any other language, primarily into Chinese or German.

Also, if you want thank us, the best way you can do that is to give us a star on github or to fork repository github/sidristij/dotnetbook.

Some days ago we announced the availability of our release candidate (RC) of TypeScript 3.4. Our hope is to collect feedback and early issues to ensure our final release is simple to pick up and use right away.

To get started using the RC, you can get it through NuGet, or use npm with the following command:

npm install -g typescript@rc

You can also get editor support by

• Downloading for Visual Studio 2017 (for version 15.2 or later)
• Following directions for Visual Studio Code and Sublime Text.

Let’s explore what’s new in 3.4!

Starting with Visual Studio 2019 Preview 4 and RC, we’ll be adjusting how C# versions are treated in .NET tooling. Read more below <cut>.

Summary of changes

Firstly, we’re adding two new Language Version (LangVersion) values: LatestMajor and Preview. Here’s how they stack up with the currently supported list of values:

How often do you get to 404 pages? Usually, they are not styled and stay default. Recently I’ve found test.do.am which interactive character attracts attention and livens up the error page.

Probably, there was just a cat picture, then they thought up eyes movement and developer implemented the idea.Now user visits the page and checks out the effect. It’s cool and pleasant small feature, it catches, then user discusses it with colleagues or friends and even repeats the feature. It could be this easy, if not:

Previously we did code reviews of large mathematical packages, for example, Scilab and Octave, whereby calculators remained aloof as small utilities, in which it is difficult to make errors due to their small codebase. We were wrong that we haven't paid attention to them. The case with posting the source code of the Windows calculator showed that actually everyone was interested in discussing types of errors hiding in it. Moreover, the number of errors there was more than enough to write an article about that. My colleagues and I, we decided to explore the code of a number of popular calculators, and it turned out that the code of the Windows calculator was not that bad (spoiler).

Today, we’re excited to announce that we are open sourcing Windows Calculator on GitHub under the MIT License. This includes the source code, build system, unit tests, and product roadmap. Our goal is to build an even better user experience in partnership with the community. We are encouraging your fresh perspectives and increased participation to help define the future of Calculator.

Blazor 0.9.0 is now available! This release updates Blazor with the Razor Components improvements in .NET Core 3.0 Preview 3.

New Razor Component improvements now available to Blazor apps:

• Improved event handling
• Forms & validation

Hi, my name is Vladislav, and I am a member of the Tarantool development team. Tarantool is a DBMS and an application server all in one. Today I am going to tell the story of how we implemented horizontal scaling in Tarantool by means of the VShard module.

Some basic knowledge first.

There are two types of scaling: horizontal and vertical. And there are two types of horizontal scaling: replication and sharding. Replication ensures computational scaling whereas sharding is used for data scaling.

Sharding is also subdivided into two types: range-based sharding and hash-based sharding.

Range-based sharding implies that some shard key is computed for each cluster record. The shard keys are projected onto a straight line that is separated into ranges and allocated to different physical nodes.

Hash-based sharding is less complicated: a hash function is calculated for each record in a cluster; records with the same hash function are allocated to the same physical node.

I will focus on horizontal scaling using hash-based sharding.

Discovering git vendor extension.

Cross-post from my medium blog: https://medium.com/opsops/git-vendor-295db4bcec3a

I would like to introduce the proper way to handle vendoring of git repositories.

What is is ‘vendoring’?

Vendoring is a way to integrate other’s work into your own. It’s the opposite of ‘linking’ against third-party library. Instead of having that library as a dependency, application uses this library as a part of own source code and keep that code ‘inside’ itself.

Normally, vendoring is done by language tooling: bundler, cargo, pip, etc. But sometimes you need to vendor something not covered by any existing toolset, or something multi-language, that it’s impossible to find the ‘core’ language tool for that.

The solution for this situation is vendoring on a git level. You have your own git repository (I call it ‘destination repo’), and you want to incorporate some other repository (I call it ‘source repo’) as a directory into your (destination repo).

The things you expect from a well-designed vendoring system (regardless of Git it is or not):

• Visibility. You want to know that some code is vendored, means it wasn’t written by committer.

In autumn, we announced we were going to expand our IT team from 49 to 250 developers. And immediately we were buried under an avalanche of questions — mostly, people were interested why a pizza chain needs so many software engineers. How did we come up with such a number? So now I want to answer that.

As announced in the previous post, on March 3 (the first Sunday of March) Mail.ru Group’s Moscow office will be hosting the third international Lua conference, Lua in Moscow 2019. See schedule details under the cut.

Why do so many programmers hate UI work? Because it is tedious. Especially, for the Web, but other types of UI are only slightly easier. Layouts, margins, paddings — neverending stream of little tweaks to make it look OK on all sane environments, and somehow this freaking button sometimes overlaps that input field. Rrrr! And yes, it should not hang on button clicks, which means a lot of asynchronous programming, which is a nightmare.

And don’t even speak about aesthetics and usability! Choose right colours, element sizes and locations, find/draw images and put them where they fit, think about user workflows — isn’t it a designers’ or Ux specialists’ job?! Leave me alone, I’m a programmer. I work with backend layers, where everything is straightforward and linear, there are no buttloads of different environments to adjust to, and design is guided by mere logic without pesky fussing with ‘user friendliness’ and ’beauty’!

Did you know you can detect if a string ends in a specific character or if it starts in one in PowerShell? Thomas Rayner previously shared on CANITPRO.NET how this can be easily done by using regular expressions or more simply know as Regex.

First, let’s talk about Reference Types and Value Types. I think people don’t really understand the differences and benefits of both. They usually say reference types store content on the heap and value types store content on the stack, which is wrong.

Let’s discuss the real differences:

• A value type: its value is an entire structure. The value of a reference type is a reference to an object. – A structure in memory: value types contain only the data you indicated. Reference types also contain two system fields. The first one stores 'SyncBlockIndex', the second one stores the information about a type, including the information about a Virtual Methods Table (VMT).
• Reference types can have methods that are overridden when inherited. Value types cannot be inherited.
• You should allocate space on the heap for an instance of a reference type. A value type can be allocated on the stack, or it becomes the part of a reference type. This sufficiently increases the performance of some algorithms.

However, there are common features:

• Both subclasses can inherit the object type and become its representatives.

Let’s look closer at each feature.

This chapter was translated from Russian jointly by author and by professional translators. You can help us with translation from Russian or English into any other language, primarily into Chinese or German.

Also, if you want thank us, the best way you can do that is to give us a star on github or to fork repository github/sidristij/dotnetbook.

Origins

Several years ago I wrote a Pascal compiler. The motivation was simple: as a teenager, I had learnt from my first programming textbooks that a compiler is a very sophisticated thing. This claim eventually became a challenge and required to be tested by experience.


ha.art.pl

First, a simplistic PL/0 compiler came into being, and later an almost fully-functional Pascal compiler for MS-DOS has grown from it. My source of inspiration was the Compiler Construction book by Niklaus Wirth, the inventor of the Pascal language. I don't care if Wirth's views are now considered obsolete and have no direct connections to the IT mainstream, or if the compiler design fashion has changed. It is enough to know that his techniques are still simple, elegant, and — last but not least — bring much fun, since it is more appealing to parse a program source with a handwritten recursive descent parser and generate the machine code, rather than to call yaccs, bisons and all their descendants.

My compiler's fate was not so trivial. It has lived two lives: the first one in my own hands, and the second in the hands of computer antiquarians from Poland.

Visual Studio 2019 pushes the boundaries of individual and team productivity. We hope that you will find these new capabilities compelling and start your upgrade to Visual Studio 2019 soon.

As you are considering this upgrade, rest assured that Visual Studio 2019 makes it distinctively easy to move your codebase from previous versions of Visual Studio. This post captures the reasons why your upgrade to Visual Studio 2019 will be pain-free.

• You can install the latest IDE side-by-side with any older VS versions
• You can continue building your C++ code with the MSVC v140 (VS 2015.3) or v141 (VS 2017) toolsets
• You can upgrade to the latest MSVC v142 (VS 2019) and maintain binary compatibility with any of your 3rd party libraries that haven’t migrated yet
• Regardless of the toolset you’re on, you get access to the full collection of OSS libraries available in Vcpkg

Every year there are a lot of articles dedicated to Valentine's Day. I also decided to get involved in this topic and create something original and unusual. The idea was to create a simple Android application with hearts that would have their physical models and interact with each other. Then I added text, sounds, particles and some other effects. The resulting app was working and quite original! In this article I will describe the creation process, as well as the capabilities and pitfalls of the libgdx library.

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Original article — "How to debug javascript in Chrome quick and easy ".

Overview

In this article, you will learn how to debug JavaScript code on front end and back end using Chrome DevTools and VS Code.