Many OCaml guides and tutorials refer to the OCaml toplevel, but what exactly is this thing? In short, the toplevel is OCaml’s Read-Eval-Print-Loop (repl) allowing interative use of the OCaml system. You can consider the toplevel an alternative to compiling OCaml into an executable. In this mode, the OCaml system is configured to repeatedly read phrases from input, typecheck, compile, and evaluate them, then print the inferred type and result value. ...

I’m a fan of Java. If you haven’t given it a chance in a while, you may not have noticed that, Java has quietly been adopting some of the best practices that make dynamic and functional languages so appealing, without sacrificing the many hundred person-years of effort that have made Java and the JVM a world-class development environment. Java is still one the world’s most popular programming languages with roughly 9 million programmers using Java. It doesn’t make sense to ignore all of that history and development effort because of a niggling feeling that Java is a little too verbose, or that XML is so last year. ...

Inversion of Control (IoC), also known as Dependency Injection (DI), allows an object to define their dependencies as constructor arguments (strictly speaking, you can set these dependencies as properties, but the examples I will use today are constructor-based). This is the inverse of the object itself controlling the instantiation or location of its dependencies, hence the name Inversion of Control. Let’s look at an example from Stackoverflow using a text editor with a spell checking component: ...

After recently setting up a new machine and going through the exercise of setting up a development environment for the nth time, I was frustrated by having to install and configure all of my plugins and dependencies to support auto-completion, syntax highlighting, and the other niceties I’ve come to enjoy with Vim. Looking for an alternative, I was drawn to Visual Studio Code (VS Code) with the VSCodeVim extension. Combining Vim key-bindings with Code’s excellent extension marketplace, I was able to recreate and in some cases improve the development environment I enjoyed as a Vim user in VS Code. This blog post continues that discovery by setting up a brand new OCaml project and development environment in VS Code. ...

This post covers some of the major features of OCaml while solving Problem 1 from Project Euler. If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23. Find the sum of all the multiples of 3 or 5 below 1000. Let’s get started on this problem by looking at the math facilities provided by OCaml. Start a new interactive session using utop. ...

opam — the OCaml Package Manager — is the tool for installing OCaml and any OCaml tools and libraries. This blog post shows us how to set-up opam to install the OCaml compiler and development tools to support your workflow. Working with Windows The OCaml tools are typically well supported on Linux, with macOS ports available of most binaries. If you are on a Windows, the best supported environment is the Windows Subsystem for Linux. ...

I was first introduced to ML through the Coursera Programming Languages course. After the initial learning curve, I was impressed by the power of the type system and the flexibility of pattern matching. I’ve been wanting to resume my education in functional programming, and am picking up OCaml for a personal project I’m working on. Diving into the OCaml ecoystem, I was drawn to Reason, a new syntax for OCaml, and BuckleScript a compiler that integrates OCaml with the JavaScript ecosystem. The relationship between Reason, BuckleScript, and OCaml can difficult to understand, leading to this blog post about the OCaml compiler pipeline that highlights the intersection between OCaml and BuckleScript. ...

Engineering, for much of the twentieth century, was mainly about artifacts and inventions. Now, it’s increasingly about complex systems. As the airplane taxis to the gate, you access the Internet and check email with your PDA, linking the communication and transportation systems. At home, you recharge your plug-in hybrid vehicle, linking transportation to the electricity grid. At work, you develop code, commit it to a repository, run test cases, deploy to production, and monitor the result. Today’s large-scale, highly complex systems converge, interact, and depend on each other in ways engineers of old could barely have imagined. As scale, scope, and complexity increase, engineers consider technical and social issues together in a highly integrated way as they design flexible, adaptable, robust systems that can be easily modified and reconfigured to satisfy changing requirements and new technological opportunities. ...

Before the Internet became a global network connecting millions of devices, it was a simple research experiment connecting a handful of institutions. In the beginning, the number of unique internet addresses could be measured in the tens. As the network expanded that number quickly grew into the hundreds and thousands and it became difficult to remember and type in IP addresses for each of these hosts. To manage the growing number of network hosts, a simple text file, called HOSTS.txt recorded each host and their IP address. To add your name to the hosts file, you needed to send an e-mail describing the changes you wanted to apply. The authority for the HOSTS.txt file would apply these changes once or twice a week and anyone who wanted to grab the updated list would periodically FTP to the canonical source, grab the latest file, and update their own list of hosts. Naturally, as this small network expanded into, and was eventually replaced by, the Internet, this solution became untenable – there were just too many hosts to keep track of, keep consistent, and to serve from a single canonical file using FTP and manual updates. HOSTS.txt did not scale. ...

Leading software companies have discovered that developing capable technology is not enough to guarantee long-term success. To stay relevant, software leaders need to develop and support the repeatable systems necessary to develop and sustain knowledge and expertise. Many organizations have taken inspiration from Spotify’s culture and adopted the concept of a guild or community of practice to connect engineers throughout the organization and steer them towards common goals. As organizations adopt this model, what is often missing is a clear understanding of the purpose of communities of practice and a repeatable process for developing the communities to their fullest potential. This post provides some guidance based on our experience developing a community of practice at Workiva, it also includes some best practices from the book Cultivating Communities of Practice. ...