Why Functional Programming Matter

What issues do we concern when implementing and maintaining systems?

One of the most concern is debugging during maintenance: "this code crashed because it observed some unexpected value."

Then, it turns out that the ideas of no side effects and immutability, which functional programming promotes, can help.

Shared mutable data is the root cause

Shared mutable data are read and updated by more than one of the methods. Share mutable data structures make it harder to track changes in different parts of your program.

An immutable object is an object that can't change its state after it's instantiated so it can't be affected by the actions of a function. It would be a dream to maintain because we wouldn't have any bad surprises about some object somewhere that unexpectedly modifies a data structure.

A new thinking: Declarative programming

There are two ways thinking about implementing a system by writing a program.

- Imperative programming: has instructions that mimic the low-level vocabulary of a computer (for example, assignment, conditional branching, and loops).

- Declarative programming: you give rules saying what you want, and you expect the system to decide how to achieve it.

Functional programming = side-effect-free + declarative programming

Functional programming exemplifies the idea of declarative programming ("just say what you want, using expressions that don't interact, and for which the system can choose the implementation") and side-effect-free which is mentioned above when using immutable objects approach.

Reference

Image result for java 8 in action

Alan Mycroft and Mario Fusco, Java 8 in Action: Lambdas, Streams, and Functional-style Programming. Part 4. Beyond Java 8.

Comments

Set up a web server for learning HTTP headers

Motivation We all follow the client-server model using the HTTP protocol for most of our web apps today. In development, we simply may have a backend API server and a frontend (web pages or mobile apps) only. However, it seemed that a proxy server is always required for production. In fact, most of the hardest issues in production come from integration. The requests and responses might be modified by the proxy server. Therefore, the understanding of HTTP protocol is one of the key skills to resolve those issues. I wanted to dive deep into HTTP with some core concepts such as caching, cookies, and CORS. I didn't intend to go quickly rather than moved slowly to have a well understanding of what I do. Prepare a server The easiest way is to use my laptop as a server then I can just use "localhost". I can also use ngrok to make my web server online. Finally, I use an online tool such as RedBot to check the HTTP headers. To make it more excited though, I deployed the app on A...

What the heck is Meteor DDP?

I was using Meteor for my messenger project. I was so curious about the real time connection. I wanted to know how exactly this mechanism works. In this post, I will go through the DDP Specification, an overview of WebSocket, and a simple demo about how to subscribe a publication of Rocket.Chat (containing a DDP server) from an external webpage. At a glance, I knew that Meteor invented a protocol called DDP which uses for handling real time connection. So then, what is DDP? "DDP (Distributed Data Protocol) is the stateful WebSocket protocol that Meteor uses to communicate between the client and the server." [1] All right! Why does DDP matter? "DDP is a standard way to solve the biggest problem facing client-side JavaScript developers: querying a server-side database, sending the results down to the client, and then pushing changes to the client whenever anything changes in the database" . [2] In order to understand deeply the protocol, I decided ...

Merging source in SVN

My team has used Primefaces for our projects. We sometimes have several branches of the projects with a new Primefaces's release. For example, we currently have a project with two branches, a branch for using Primeface 4.0, a trunk for using Primeface 5.0, and we are working these parallel branches. Our project looks like the following: - myProject - branches + primefaces4 + tag + trunk (primefaces5) My problem is how to copy the same source from the trunk to the branch "primefaces4". That is where SVN Merging can help! Here is the steps those I have conducted in my project. Step 1 : open the project with the branch "primefaces4" Step 2 : Team > Merge... Chose the trunk's URL. For example: http://192.168.9.10/svn/myProject/trunk Step 3 : Select the revision from "trunk" to merge. For example: +--revision--+--date--------+--author----+--comment---+ + 10 + 03.10.2014 + vanhuong + f1: part 3 + + 9 ...

A Template for Software Engineering Standards

Software engineering standard template A well-structured standard acts as a blueprint that guides engineers in their daily tasks and long-term goals. Below, I will outline a template for creating a comprehensive software engineering standard. Header The header serves as the document's identifier. It contains the following: Authors : The people who have contributed to the creation of the standard. Created Date : The date when the document was initially created. Version : The version of the standard. It is typically updated with significant changes. Status : The current status of the document, whether it's in draft, in-review, or official. Next Review Date : The date when the standard will be reviewed for relevancy and accuracy. Table of Contents A table of contents provides an overview of what the document contains, making it easier for readers to navigate through the document. Body The body of the standard comprises: Values : The core beliefs that guide the decision-maki...

Monday vhandit #2

Introduction to OpenLDAP directory service "A directory is a specialized database specially designed for searching and browsing, in addition to supporting basic lookup and update functions" A directory service can be local, providing a restricted context; or global, providing service to a much broader context. Curlie is a good example of a directory service. LDAP (Lightweight Directory Access Protocol) is a protocol for accessing directory services , specifically X.500-based directory services. OpenLDAP is an open-source implementation of LDAP. Writing system software: code comments I have read Clean Code (by Uncle Bob) and I thought that I should void comments since the code it explains its implementation itself. That is right but not always true. In this post, the author categorized the comments into 9 types. Only "trivial comments" and "backup comments" are the ones that should be avoided. I myself agree with "writing good comments is harder tha...

vhandit

Search This Blog