Author Archives: Victor Laskin

Templates as first-class citizens in C++11

templates as citizens

C++11 treats functions as first-class citizens and this gives us ability to construct a lot of nice things as design patterns borrowed from functional languages. Meanwhile C++ has very powerful template metaprogramming. This post is aimed to make templated functions closer to first-class citizens, and to construct some simplicity and beauty which you can get from it.

Also here will be implementation for currying of such functions! If you don’t know what currying is – just remember std::bind.

And to make it shine we’ll add piping. (This article will improve some ideas from post about functional piping ). This step is optional and you can replace such piping with commas and function calls.

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C++11: Implementation of list comprehension in SQL-like form

list comprehension

List comprehension in functional languages is the name of list constructor syntax, which is similar to set-builder notation from math.

What are the benefits of using list comprehension? One is readability, and the other one is the fact of decoupling iteration from actual construction. We could even hide parallel execution under the hood of list comprehension. Also by adding additional options to such declaration we could make the list construction a lot shorter.

If we look closer at list comprehension’s syntax, it will remind of one another very familiar thing – SQL select! Output expression, input set, predicates are equivalent to select, from, where sequence (of course not exactly, but they are very alike). Ok, let’s implement such syntax sugar using C++11 (without boost and LINQ-like libs).

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C++11 functional decomposition – easy way to do AOP

This post is about making functional decomposition from perspective of Aspect Oriented Programming using C++11. If you are not familiar with ideas of AOP don’t be afraid – it’s rather simple concept, and by the end of this post you will understand the benefits of it.

You also can treat this post just as example how to use high-order functions in C++11.

In short – AOP tries to perform decomposition of every business function into orthogonal parts called aspects such as security, logging, error handling, etc. The separation of crosscutting concerns. It looks like:
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Small presentation of my cross-platform engine for mobile and desktop applications

I made small presentation about my cross-platform engine for mobile and desktop applications. Codename Kobald. Click on image to play it in new window (use arrows and space to move through):

Screenshot 2015-01-21 21.53.14

This is not-so-technical presentation and main info about engine will come later as separate post.

Functional pipeline in C++11

c++11 pipeline

I stumbled upon this nice blog post – pipable functions in C++14. This is realy fun idea as its usage plain for anybody who is familiar with unix pipelines. So i tried to use it in C++11 (without boost) from slightly different angle to make it more real-life concept.

First sample (fun, but not so interesting):

Second sample (functional style array processing):

Simple and short implementation is under the cut…

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10 ways to not shoot yourself in the foot using C++11

Within C++, there is a much smaller and cleaner language struggling to get out (Stroustrup)

The following text could be modified – current rev.1.0

Very often i hear from java/erlang/etc people that C++ is so bad that it is very unwise to use so-old-school language now, when we have more ‘safe’ higher level languages. Everybody heard about foot-shooting using C++.  What about C++11?

Bjarne said that C++11 feels like whole new language and, at first, i did not take it seriously as modifications looked more as minor additions (especially for boost users). Now i changed my mind – using new features combined together can transform your way of coding into new form. I’m talking not about adding new features to your code, but about changing your coding style.

How not to shoot yourself in the foot? Here is the list of my rules to make the C++ coding life sweet and easy. This is simple convention to follow and can be adopted very fast. Not only it gives more stable implementation but also more clean and understandable design.

This convention is composition of Scott Meyers rules, Functional programming ideas and reducing-complexity ideology by Steve McConnell.

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Writing custom protocol for nanomsg

Custom protocol for nanomsg

Nanomsg is next version of ZeroMQ lib, providing smart cross-platform sockets for implementation of distributed architectures. Here you can find basic examples of included protocols (communication patterns). Lib is simple (written in pure C) and does not have any dependencies like boost. And as this is at least 3rd iteration from same author you can expect some quality/performance here.

This is kind of solution for the hell of writing of your own serious socket server. If you already had such experience you should understand the range of problems which are not so obvious at start. But here we expect to skip all such problems and go straight to processing messages. Lib handles automatic reconnection in case of link disconnects, nonblocking receiving/sending, sockets which can handle large set of clients, etc. All this seems like perfect solution for server-side inner transport of fast distributed architectures.

But i also want to try it outside. The basic communication patterns (PAIR, BUS, REQREP, PUBSUB, PIPELINE, SURVEY) may fit large set of inner server transport schemes, but there are some minor limits in current implementation for client side application. I mean limits of protocols, not the lib itself.

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Easing functions for your animations

Today’s design guidelines state that all animated movement inside your application should contain so called easing. You can read this section from google material design. If your UI-framework does not contain implementations for standard set of easings you can create your own.

Easing functions

Easing functions

Here is place where you can check out animated plottings for basic easing functions. And here you can find source code for them in several languages (JS,Java,Lua,C#,C++,C).

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How to make simple CQRS implementation without Event Sourcing

Here I will try to describe the concept of CQRS without event sourcing based on some other principle instead. The concept to organise your data and messages to create scalable and reliable CQRS/Messaging-based architecture without additional complexity from event store.

CQRS - MVC

At first here is small introduction on what SQRS is. I suppose you are familiar with MVC model and use it on daily basis. And i suppose you understand benefits of separation your code into separate modules.

CQRS – Command-Query Responsibility Segregation. CQRS just separates model into 2 separate parts – READS model and WRITES model. They also can be referenced as Query model and Command model.

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Dockerfile example how to compile libcurl for Android inside Docker container

If you never heard of Docker be sure to check it out as fast as possible. There are lot of publications out there. At first it looks like another virtualisation software but it is actually more like new paradigm. Someone may call it very advanced chroot, someone may call virtual containers with version control and building scripts, and so on. I like it as the idea of application-centric containers – your application can keep whole operating system as a coating and its making perfect separation from outside influence. As well you can easily reproduce production process environment at another location. It makes virtualisation easy and fun.

Libcurl in docker

Almost everything can be done inside containers now. Recently i had to recompile curl for Android as static lib using latest NDK toolchain. Its not so complicated to do on your local machine (if it is not Windows) but now there is a more clean way to do this time-wasting operation. You can go to digital ocean, create droplet with Docker and using Dockerfile from the end of this post compile it while drinking coffee.

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