Today I'll write an implementation in JavaScript of Zeller's Congruence, a simple and elegant little formula to carry out the seemingly complex task of calculating the day of the week (Monday, Tuesday etc.) from a date.
Continue readingCalculating any Term of the Fibonacci Sequence Using Binet’s Formula in JavaScript
You can calculate the Fibonacci Sequence by starting with 0 and 1 and adding the previous two numbers, but Binet's Formula can be used to directly calculate any term of the sequence. This short project is an implementation of that formula in JavaScript.
Continue readingEstimating Pi in JavaScript
Pi is an irrational number starting off 3.14159 and then carrying on for an infinite number of digits with no pattern which anybody has ever discovered. Therefore it cannot be calculated as such, just estimated to (in principle) any number of digits, and in this post I will implement a few of the many methods for doing so in JavaScript.
Continue readingFinding Prime Numbers with the Sieve of Eratosthenes in JavaScript
Prime numbers have been understood at least since the Ancient Greeks, and possibly since the Ancient Egyptians. In modern times their study has intensified greatly due to their usefulness, notably in encryption, and because computers enable them to be calculated to a massively higher level than could be done by hand.
The best know (and according to Wikipedia still the most widely used) method for identifying them is the Sieve of Eratosthenes, which I will implement here in JavaScript.
Continue readingThe Soundex Algorithm in JavaScript
Soundex is one of a number of phonetic algorithms, assigning values to words or names so that they can be compared for similarity of pronounciation. It is probably the best know such algorithm as it is built in to most major RDBMSs, as well as PHP and other languages. Here I will write an implementation in JavaScript.
It doesn't take much thought to realise that the whole area of phonetic algorithms is a minefield, and Soundex itself is rather restricted in its usefulness. In fact, after writing this implementation I came to the conclusion that it is rather mediocre but at least coding it up does give a better understanding of how it works and therefore its usefulness and limitations.
Wikipedia has a surprisingly brief article on the topic Soundex on Wikipedia which you might like to read.
Continue readingGreat Circle Distances in JavaScript
The shortest distance between two locations on the surface of Earth (or any planet) is known as the Great Circle Distance. Except for relatively short distances these cannot be measured on a map due to the distortion and flattening necessary to represent a sphere on a flat plane. However, the calculation of the Great Circle Distance from two coordinates is simple, although I suspect generations of midshipmen might not have agreed. In this post I will write a short JavaScript application to calculate the distance from London to various other cities round the world.
Continue readingShould You Learn Data Structures and Algorithms?
You could reasonably argue that data structures and algorithms are at the heart of computer science. This leads to the widespread belief that they are also at the heart of software development and that a detailed or even profound knowledge of them is necessary to be a decent programmer. I believe that while it doesn't do any harm to learn them in depth it is not the best use of your time.
Continue readingIDElessness: hand-crafting code in a text editor
Should you always use an IDE to write software? Is it sometimes good to get back to a simple text editor and command lines tools?
Continue readingHSL GUI in Python
I recently wrote a post on RGB/HSL Conversions in Python and as a follow-up I decided to put together a simple Tkinter application which enables users to display a colour by selecting any combination of hue, saturation and lightness.
This application is only a toy but playing with it for a few minutes does give an intuitive understanding of the HSL system, and reinforces my conviction that it is easier to comprehend than RGB. And if you have never used Tkinter this project also provides a simple introduction to the topic.
Continue readingRGB/HSL Conversions in Python
A while ago I wrote a post called Colour Converter in C about converting RGB (red/green/blue) values to HSL (hue/saturation/lightness) and back again. As part of a project which I am planning I need to be able to do the same in Python and was intending to re-write the C in Python, or probably Cython. However, I then found a module called colorsys in an obscure corner of the Python Standard Library. This module includes functions to do the conversions I will need, and in this post I will demonstrate using them to create an array of HSL values from a Pillow image, and then convert these back to RGB to create a new identical image.
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