Computing: page 2
To make the construction and maintenance of more advanced types easier it can be helpful to write some tests that ensure their correct function. This sounds a little easier than it turns out to be. As part of the ecosystem for TypeScript Microsoft have written and released the dtslint tool. It can be used to link and compile TypeScript types for static analysis and mostly serves to keep the @types/* packages in line. Read more ⇒
As TypeScript applications get more complex so do the types required to describe it. There are a number of built-in types that can be used for this purpose or combined to create more specialised types. What I term modifying types such as Partial and Required are included in the language and I will quickly cover these first to warm up for the deeper types we’ll address later. This article will quickly move on to focus on the slightly more advanced types beginning with Extract. Read more ⇒
TypeScript constructors and generic types
I have recently found myself needing a type for class constructors that is at once generic and tight enough to ensure a genuine constructor. This is useful in situations where you must handle a variety of classes - those that come from other libraries or applications that you cannot control. When writing your own dependency injection container or some other generalised library you cannot know what class constructors might be passed in. Read more ⇒
The lambda calculus for developers
This will be a quick introduction to the lambda calculus syntax, alpha (α) equivalence and beta (β) reduction. What does a lambda look like? I am going to use the identity function as an example for the simplicity it provides. This can be expressed as a lambda function with the notation λx.x. It is a function that when given an argument outputs that argument as its return value. You can also have multiple arguments with a lambda like λxy. Read more ⇒
Search and replace with confirmation in Bash
Automated search and replace can be very handy although there are occasions where a human needs to get involved on some of the decisions. If the search term isn’t unique or appears as part of other words or something like that. When this is the case you’ll want a confirm step where you can approve each replacement before it happens. With very little work we can achieve this using a combination of vim and grep. Read more ⇒
PHP and immutability: objects and generalisation - part three
In the last article we learnt how to create modified copies of an immutable in PHP. This one is going to tackle an issue I have hitherto skirted around and avoided. Objects in immutable data structures. This article is part of a series I have written on the topic of immutability in PHP code: Part one - a discussion of caveats and a simple scalar handling immutable Part two - improve the process of creating modified copies of the immutable Part three - objects in immutable data structures and a generalised immutable implementation Also available in Русский (Russian): Read more ⇒
PHP and immutability: modified copies - part two
In the last article we learnt how to create an immutable data structure in PHP. There were a few issues to work through, but we got there in the end. Now onto making the immutable class more useful and easier to create modified copies. Note that these are copies and not modifications, in-place, to the original objects. This article is part of a series I have written on the topic of immutability in PHP code: Read more ⇒
PHP and immutability: difficulties and scalars - part one
Being a weakly typed dynamic language, PHP has not really had the concept of immutability built into it. We’ve seen the venerable define() and CONSTANTS of course, but they’re limited. Whilst PHP does ship with an immutable class as part of it’s standard library, DateTimeImmutable, there is no immediately obvious method to create custom immutable objects. This article is part of a series I have written on the topic of immutability in PHP code: Read more ⇒
Alter a MySQL column in all databases
When you have a series of applications all running the same database structure it can be annoying to roll out schema updates across all the databases. If you’ve got migrations then great - script their deployment, but when you’re dealing with an old legacy application you probably don’t have the luxury. I was firmly in the latter class of devops when working on a project a couple of years ago so I wrote a handy little snippet of SQL to help me out. Read more ⇒
Email me when the file changes
It is important to ensure that Google does not index sites whilst they are still on a staging environment, but you cannot lock it down completely - how would your clients proof it? So I run a simple global rewrite rule in Apache that redirects all requests for robots.txt to a central disallow all response. This works great and Google appears to honour the rule as one would hope. What happens though when something about that central file changes? Read more ⇒