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

BIRT - Fix the size of an image

I use a dynamic image as a logo my report in pdf. At the beginning, I use table to align the logo in left or right. I meet a problem with some images with a large width or height. My customer requires that the logo should be displayed in original size. These following steps solves my problem: 1. Use Grid instead of Table 2. Set Grid "Height" is 100% and "Width" is blank 3. Set "Fit to container" for images are "true". Download the the template here .

Make simple music program with beep(freq, duration) with Pascal

Pascal is my first programing language when I have studied in high school. It was really exciting for me. :) The Pascal programming language was created by Niklaus Wirth in 1970. It was named after Blaise Pascal, a famous French Mathematician. It was made as a language to teach programming and to be reliable and efficient. Pascal has since become more than just an academic language and is now used commercially . I tried to make a simple music program by using Lazarus IDE on MS Window 7, 64-bit. It frustrated me a few times how difficulty to use Sound command to make a sound. Sound did not work on my compiler and my platform anymore. So far, I just could use beep(freq, duration) from window unit to implement my work. Here is my code. ;) program mysong; uses Windows, crt; const C: Integer = 512; { x = A * EXP(LN(2)/12)} C_: Integer = 542; D: Integer = 574; D_: Integer = 608; E: Integer = 644; F: Integer = 682; F_: Integer = 723; G: Integer = ...

Styling Sort Icons Using Font Awesome for Primefaces' Data Table

So far, Primefaces has used image sprites for displaying the sort icons. This leads to a problem if we want to make a different style for these icons; for example, I would make the icon "arrow up" more blurry at the first time the table loading because I want to highlight the icon "arrow down". I found a way that I can replace these icons with Font Awesome icons. We will use "CSS Pseudo-classes" to achieve it. The hardest thing here is that we should handle displaying icons in different cases. There is a case both "arrow up" and "arrow down" showing and other case is only one of these icons is shown. .ui-sortable-column-icon.ui-icon.ui-icon-carat-2-n-s { background-image: none; margin-left: 5px; font-size: 1.1666em; position: relative; } .ui-sortable-column-icon.ui-icon.ui-icon-carat-2-n-s:not(.ui-icon-triangle-1-s)::before { content: "\f106"; font-family: "FontAwesome"; position: ...

Tip for resolving the compile errors when importing a Maven project in Eclipse

Sometimes, I import a existing Maven project into Eclipse and I get some compile errors related to "pom.xml", "facet version of Web", and so on. It was really frustrating me because I even cleaned, built and updated the project many times but the errors still occurred. I accidentally found the following steps to resolve this issue but honestly I still don't know why. Step 1 : Delete the project that met the compile errors in Eclipse, but don't delete it on disk. Step 2 : Open the project (by Windows Explorer if you use Windows) and remove file/folder ".classpath", ".settings" and ".project" . Step 3 : Import the project back into Eclipse. ---^0^--- Maven is a build automation tool used primarily for Java projects. Eclipse is an integrated development environment (IDE).

Math fundamentals and Katex

It was really tough for me to understand many articles about data science due to the requirements of understanding mathematics (especially linear algebra). I’ve started to gain some basic knowledges about Math by reading a book first. The great tool Typora and stackedit with supporting Katex syntax simply helps me to display Math-related symbols. Let’s start! The fundamental ideas of mathematics: “doing math” with numbers and functions. Linear algebra: “doing math” with vectors and linear transformations. 1. Solving equations Solving equations means finding the value of the unknown in the equation. To find the solution, we must break the problem down into simpler steps. E.g: x 2 − 4 = 4 5 x 2 − 4 + 4 = 4 5 + 4 x 2 = 4 9 x = 4 9 ∣ x ∣ = 7 x = 7 or x = − 7 \begin{aligned} x^2 - 4 &= 45\\ x^2 - 4 + 4 &= 45 + 4\\ x^2 &= 49\\ \sqrt{x}&=\sqrt{49}\\ |x| &= 7\\ x=7 &\text{ or } x=-7 \end{aligned} x 2 − 4 x 2 − 4 + 4 x 2 x ∣ x ∣ x = 7 = 4 5 = 4 ...

vhandit

Search This Blog