Programming *

A few days ago 0xd34df00d has published the translation of the article, describing the possible information about some function if we use it as a "black box", not trying to read its implementation. Of course, this information is quite different from language to language; in the original article, four cases were considered:

• Python — dynamic typing, almost no information from signature, some hints are gained by the tests;
• C — weak static typing, a little more information;
• Haskell — strong static typing, with pure functions by default, a lot more information;
• Idris — dependent typing, compiler can prove the function correctness.

"Here's C and there's Haskell, and what about Rust?" — this was the first question in the following discussion. The reply is here.

Have you ever looked for a flat? Would you like to add some machine learning and make a process more interesting?

At the last Tech Train IT festival, we met the legendary John Romero, who designed and developed the iconic Wolfenstein 3D, Doom, and Quake. We talked about whether game developers need soft skills, which working tools to pay attention to, and which co-founder of Id Software's favorite toys are. Questions were asked by Nikita Tsaplin, the founder of RUVDS.


→ Text and video in Russian

Talking to people at conferences and in comments to articles, we face the following objection: static analysis reduces the time to detect errors, but takes up programmers' time, which negates the benefits of using it and even slows down the development process. Let's get this objection straightened out and try to show that it's groundless.

It is a new selection of tips and tricks about Python and programming from my Telegram-channel @pythonetc.

← Previous publications


If an instance of a class doesn’t have an attribute with the given name, it tries to access the class attribute with the same name.

>>> class A:
...     x = 2
...
>>> A.x
2
>>> A().x
2

Apache Dubbo is one of the most popular Java projects on GitHub. It's not surprising. It was created 8 years ago and is widely applied as a high-performance RPC environment. Of course, most of the bugs in its code have long been fixed and the quality of the code is maintained at a high level. However, there is no reason to opt out of checking such an interesting project using the PVS-Studio static code analyzer. Let's see how it turned out.

In this article, I would like to propose an alternative to the traditional test design style using functional programming concepts in Scala. This approach was inspired by many months of pain from maintaining dozens of failing tests and a burning desire to make them more straightforward and more comprehensible.

Even though the code is in Scala, the proposed ideas are appropriate for developers and QA engineers who use languages supporting functional programming. You can find a Github link with the full solution and an example at the end of the article.

Surely you've heard the expression «bug hunting» many times. I dare to assume, you won't mind earning one or two hundred (or even thousand) dollars by finding a potential vulnerability in someone's program. In this article, I'll tell you about a trick that will help analyzing open source projects in order to find such vulnerabilities.

In this article, we will consider the process of setting up a React Native environment using expo-cli, Typescript, and Jest.
Typescript will help us avoid development mistakes and write a more efficient mobile application.

Modern tools allow integrating Typescript into the development environment. We can also use VS Code that supports Typescript.

Integration with React Native will give us the opportunity to use the auto-completion service, code navigation, and refactoring.

Expo is a toolkit that simplifies the creation of native React applications. This tutorial will give you an idea of how you can quickly create native React applications using Expo.

Many programmers struggle when using formal methods to solve problems within their programs, as those methods, while effective, can be unreasonably complex. To understand why this happens, let’s use the model checking method to solve a relatively easy puzzle:

Conditions

You’re in a hallway with seven doors on one side leading to seven rooms. A cat is hiding in one of these rooms. Your task is to catch the cat. Opening a door takes one step. If you guess the correct door, you catch the cat. If you do not guess the correct door, the cat runs to the next room.

Developer Christophe Verdot shares his experiences of recently taking the online course ‘Mastering Web 3.0 with Waves’.



What is your background? What motivated you to take the course?

I’ve been a web developer for about 15 years, working mostly as a freelancer.

It is a new selection of tips and tricks about Python and programming from my Telegram-channel @pythonetc.

← Previous publications


You can’t mutate closure variables by simply assigning them. Python treats assignment as a definition inside a function body and doesn’t make closure at all.

Hi, my name is Michael Kapelko. I have been developing software professionally for more than 10 years. I develop games and game development tools in my spare time.

This article describes my first durable application for desktop PCs: PSKOV static site generator.

Durability

A durable application is an application that functions without a single change on operating systems released in years 2010-2030. In other words, a durable application has backward compatibility of 10 years and has the stability to run for 10 years. Actually, PSKOV runs even under Windows 2000, so PSKOV has backward compatibility of 19 years.

User interfaces of modern enterprise applications are quite complex. You, as a developer, often need to implement in-app navigation, validate user input, show or hide screens based on user preferences. For better UX, your app should be capable of saving state to the disk when the app is suspending and of restoring state when the app is resuming.

ReactiveUI provides facilities allowing you to persist application state by serializing the view model tree when the app is shutting down or suspending. Suspension events vary per platform. ReactiveUI uses the Exit event for WPF, ActivityPaused for Xamarin.Android, DidEnterBackground for Xamarin.iOS, OnLaunched for UWP.

In this tutorial we are going to build a sample application which demonstrates the use of the ReactiveUI Suspension feature with Avalonia — a cross-platform .NET Core XAML-based GUI framework. You are expected to be familiar with the MVVM pattern and with reactive extensions before reading this note. Steps described in the tutorial should work if you are using Windows 10 or Ubuntu 18 and have .NET Core SDK installed. Let's get started! Source code of the app described in this tutorial is available on GitHub.

When mulling over the best programming language to use for data science, Python and R ring a bell (very quickly). While there are a lot of languages like C, C++, Java, Julia, Perl, and Scala, it's protected to state that Python and R are the harbingers in data science.

While a great deal of data researchers will discuss the customary shortcomings like data wrangling in R or data representation in Python, ongoing improvements like Altair for Python or R have adequately reacted to these shortcomings.

So which one would it be a good idea for you to decide for your next data investigation venture?

R has been ruling this space for a long time now. This bodes well as this programming language was explicitly intended for analysts.

In order to verify the quality of software, you have to use a lot of different tools, including static and dynamic analyzers. In this article, we'll try to figure out why only one type of analysis, whether static or dynamic, may not be enough for comprehensive software analysis and why it's preferable to use both.

Today at Xamarin Developer Summit, we announced XAML Hot Reload for Xamarin.Forms, which enables you to make changes to your XAML UI and see them reflected live, without requiring another build and deploy.

XAML Hot Reload for Xamarin.Forms speeds up your development and makes it easier to build, experiment, and iterate on your user interface. And this means that you no longer have to rebuild your app each time you tweak your UI – it instantly shows you your changes in your running app!

When your application is compiled using XAML Hot Reload, it works with all libraries and third-party controls. It will be available for iOS and Android in Visual Studio 2019 and Visual Studio 2019 for Mac. This works on all valid deployment targets, including simulators, emulators, and physical devices.

XAML Hot Reload will be available later in 2019, but you can sign up to to participate in the preview phase:

Sign Up for the Preview Now

Last time, we used SFINAE to detect whether a type had a definition, and we used that in combination with if constexpr and generic lambdas so that code could use the type if it is defined, while still being accepted by the compiler (and being discarded) if the type is not defined.

However, our usage had a few issues, some minor annoyance, some more frustrating.

• You had to say struct all the time.
• If the type didn’t exist, the act of naming it caused the type to be injected into the current namespace, not the namespace you expected the type to be in.
• You must use the struct technique with an unqualified name. You can’t use it to probe a type that you didn’t import into the current namespace.

We can fix all three of the problems with a single solution: Predeclare the type in the desired namespace.

Let’s begin from a far distance with the goal that the novices can see how the file described in the article works. To work the website on the Internet, you need not just a PC and access to the network, yet additionally, extraordinary programming introduced on it, which gives access to information utilizing the HTTP and HTTPS conventions. This product is the web server. There are different sorts of web servers, however, the most widely recognized is Apache. It is based on the open-source code, free, is continually being improved and enhanced, compatible with many scripts, and works on almost all platforms, including Windows, Linux, Netware 5.x.

Great Visual Studio extensions share a few key features that sets them apart from the rest. They look and feel well crafted, are performant and reliable, do what they advertise to perfection, and blend in naturally among Visual Studio’s own features.

To make it easier to write great extensions, we’ve worked with the extensibility community to come up with a simple checklist to follow. There’s even a GitHub issue template you can use so you remember to go through the checklist.