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Make it easier to get finished: Interview with John Romero, developer of Doom
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The art of creating computer programs
>>> class A:
... x = 2
...
>>> A.x
2
>>> A().x
2
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.
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.
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.struct
all the time.struct
technique with an unqualified name. You can’t use it to probe a type that you didn’t import into the current namespace.Some time ago, in a discussion on one of SObjectizer's releases, we were asked: "Is it possible to make a DSL to describe a data-processing pipeline?" In other words, is it possible to write something like that:
A | B | C | D
and get a working pipeline where messages are going from A to B, and then to C, and then to D. With control that B receives exactly that type that A returns. And C receives exactly that type that B returns. And so on.
It was an interesting task with a surprisingly simple solution. For example, that's how the creation of a pipeline can look like:
auto pipeline = make_pipeline(env, stage(A) | stage(B) | stage(C) | stage(D));
Or, in a more complex case (that will be discussed below):
auto pipeline = make_pipeline( sobj.environment(),
stage(validation) | stage(conversion) | broadcast(
stage(archiving),
stage(distribution),
stage(range_checking) | stage(alarm_detector{}) | broadcast(
stage(alarm_initiator),
stage( []( const alarm_detected & v ) {
alarm_distribution( cerr, v );
} )
)
) );
In this article, we'll speak about the implementation of such pipeline DSL. We'll discuss mostly parts related to stage()
, broadcast()
and operator|()
functions with several examples of usage of C++ templates. So I hope it will be interesting even for readers who don't know about SObjectizer (if you never heard of SObjectizer here is an overview of this tool).