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In our previous post on mutability, we discussed the fact that time was to be taken into consideration when mutability was involved. We observed objects lifetime as instant by instant, computing and assigning objects states for each instant. Another way to look at time is to consider the state as a discrete set of values. From this perspective, we can see the time as being an infinite sequence, a stream, and the state can also be seen as a stream computed out of time.
PowerShell is versatile command line shell which comes with a powerful scripting language. It is now even more available than before with the new PowerShell Core which makes it available on Linux. Even though the main commands in the scripting language have been around for ages, I always see myself having to re-learn how to use it every time I need to write a script.
Mutability is a topic of high interest in the view of developers adventuring themselves in functional programming languages where it is generally unwelcomed and, in some instances, made voluntarily hard to implement. In contrast, object oriented programming has assignment at its core. Objects are represented as entity with a state modifiable over the lifetime of the application.
Data abstraction allows us to think about complex systems in term of their properties rather than their implementations. Reasoning in term of properties provides a ground of assumptions which can be used to create new systems. In common programming languages, abstraction is present everywhere, as interfaces, as abstract and regular classes, as functions, as function signatures, as user interfaces, etc. All of theses tools provide a way to build layers of abstraction which we can work on top of to create new functionalities by manipulating data on the appropriate layer.
Few weeks ago we saw how to configure CloudWatch to monitor upstream response time from logs. We create a CloudWatch configuration which allowed us to create metrics by parsing the logs and create a dashboard out of it. Building up from there, today we will see how we can monitor disk used space and trigger an alarm when the remaining disk space is critical.
Floyd’s Tortoise and Hare is a cycle detection algorithm operating on a linked list. The algorithm is based on two pointers, the tortoise and the hare, moving on the linked list at a different speed. The algorithm can be used to find cycle existence, deduces the beginning of the cycle, and the length of a cycle. Today we will explore the mathematical proof behind the algorithm and we will implement it in Racket.
Last week, we briefly looked into the Y Combinator also known as fixed-point combinator. Today we will explore more on the territory of fixed-points by looking at what a fixed-point is, and how it can be utilized with the Newton’s Method to define an implementation of a square root procedure.
Recursion refers to the property of a function to be defined in term of itself. The Fibonacci sequence is a great example of a recursive problem where a Fibonacci number is calculated from a combination of precedent Fibonacci numbers. Recursion can be implemented in many forms, it is even possible to implement recursion without explicit self calling. Today we will look at different implementations of Fibonacci and discover their properties.
Last week a colleague of mine introduced me to the concept of continuation in Racket (the best of Scheme and Lisp - at least that is what racket-lang.org states). I knew about the existence of Lisp but I never really paid attention to what it provided as language features. So I took the bite and started to read the post shared to me on continuations, written by Matt Might and oh boy… was I confused. Everything about the code confused me, the notation, the syntax, and of course the flow of the program itself. What I understood was that this piece was implementing Exceptions by using continuations which was enough to make me want to understand it.
Property-based testing is a testing method where a property of our system is tested against multiple datasets. Today we will see how we can create property tests using Hypothesis in Python.
Flask is a microframework for python providing building blocks to compose websites and web API quickly. It has a vast ecosystem driven by open source libraries maintained and used by many developers. Today we will see how we can setup a simple todo web API using Flask and how we can setup OpenAPI 3.0 (OAS3 - previously known as Swagger).