Anil Madhavapeddy – Unikernels: Functional Infrastructure with Mirage OS


Anil captivates the crowd with his talk on Mirage OS.

Last week, we had the privilege of hosting a very special guest speaker, Anil Madhavapeddy. You already know him as one of the authors behind “Real World OCaml: Functional programming for the masses”.

Anil showed us some neat developments from the Mirage OS project. Topics of interest included: an informal demonstration of OCaml Unikernels, a tutorial about operating system aspects, and a walkthrough of the TLS stack. Magnus Skjegstad gave us a demo of Jitsu which can spin up servers within milliseconds just-in-time as a request arrives. Anil also showed us the Bitcoin Piñata and invites programmers to tackle this challenge for a chance at free Bitcoins!

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Anil talks about Unikernels.

Below is a video of the entire talk for your enjoyment.

Those who came out to our event also had the chance to meet other OCaml enthusiasts, munch on some food, partake in some drinks, and bask in our uniquely painted officeWe’d like give a big thanks to Anil once again for making the long trip and being awesome as usual.

Thanks to everybody who came out and hope to see you at the next OCaml Meetup.


Algebraic Data Types

Algebraic data types are the fundamental building blocks of programs in ML-style languages like Haskell and OCaml. Since they play such an important role in these languages, it is well worth understanding how they work and where they come from—at first, the design may feel a bit arbitrary, but in reality it flows naturally from a reasonable starting point.

Algebraic data types are made up of two components: products (also known as structs, records or tuples) and variants (also known as tagged unions, sums or coproducts). Let’s take a look at each of these in turn, how they can be combined and how they’re related.


Products are a construct that appears in most programming languages: it’s a type that contains multiple values. The simplest example in OCaml would be a pair (just like an ordered pair in mathematics):

# let pair = (1, 2);;
val pair : int * int = (1, 2)

This pair has the type int * int which means it has two members, both integers. In prose rather than code, this is often written as int × int because it corresponds to a cross-product of sets. Fundamentally, we can do two interesting things with a pair: get the first element or get the second element:

# let first (x, y) = x;;
val first : 'a * 'b -> 'a = <fun>
# let second (x, y) = y;;
val second : 'a * 'b -> 'b = <fun>

In OCaml, pattern matching makes the definitions pretty visual. The functions first and second are often abbreviated as fst and snd or π₁ and π₂ (π is used because these are projection functions).

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