…and two practical applications… The Y Combinator is an important result in theoretical computer science.1 In this essay, after a brief review of the work we’ve already done on the Mockingbird, we’ll derive the Why Bird, known most famously…
SINGER I’m a lumberjane and I’m OK I sleep all night and I code all day She’s a lumberjane and she’s OK She sleeps all night and codes all day I write clean code, I mentor youth I go to the lavatory On Wednesdays I race bicycles Mine’s espr…
In Why Recursive Data Structures? we used multirec, a recursive combinator, to implement quadtrees and coloured quadtrees (The full code for creating and rotating quadtrees and coloured quadtrees is below). Our focus was on the notion of an…
Unfolded, © 2011 Regulla, Some rights reserved Anamorphisms are functions that map from some object to a more complex structure containing the type of the object. For example, mapping from an integer to a list of integers. An integer is our…
In some programming languages, there is a style of “monkey-patching” classes in order to add convenience methods. For example, let’s say that we’re using Ruby on Rails, and we have an array called chain_of_command. Although Ruby’s Array cla…
We’ve previously looked at using ES.later method decorators like this:1 The wrapWith function takes an ordinary method decorator and turns it into an ES.later method decorator. This is not necessary in production, as you can write your deco…
Writing higher-order functions in JavaScript is a long-established practice: A higher-order function is a function that takes one or more functions as arguments, returns a function, or both. For example, compose is a higher-order function t…
Nota Bene: All of the examples in this essay require ECMAScript-6, and were tested with the Babel transpiler. You can integrate Babel into your toolchain, or copy and paste the examples into its REPL in your browser. Many objects in JavaScr…
In our code so far (Destructuring and Recursion in ES-6 and Tail Calls, Default Arguments, and Excessive Recycling in ES-6), we have used arrays and objects to represent the structure of data, and we have extensively used the ternary operat…
In JavaScript, anywhere you find yourself writing: You can usually substitute just foo. For example, this code: This understanding is vital. Without it, you can be led astray into thinking that this code: …Is just a funny way of writing a f…
One of JavaScript’s defining characteristics is its treatment of functions as first-class values. Like numbers, strings, and other kinds of objects, references to functions can be passed as arguments to functions, returned as the result fro…
As programmers, it is our job to build software out of abstractions. Logic gates are connected to form a “Von Neumann Computer.” An assembler creates an interface that can be programmed with instructions like MOV 12345, 567890. A compiler l…