Thoughts on Julia

I have been playing around with the Julia programming language for about a week. I like it. It has a easy to read syntax, and makes sense.

What surprised me the most was after an afternoon I had submitted two PRs on GitHub for libraries in the HTTP stack. It’s not normally the case that I can get my head around a language that fast. Ok, my contribution was small, and I have by no means mastered the language.

The Good

(Edit) First of all I’d like to say how responsive and supportive the Julia community are. This is probably the most important point.

I like the syntax, for example:

function foo(z)
  for x in z

type Point

point = Point(1,2)
point.x = 3

Nice language features including:

  • Destructuring assignment
  • Coroutines
  • Callback functions have a slightly odd, but nice syntax
  • Optional type system
  • …lots more

The callback syntax looks like this:

function bar(callback::Function)

bar() do 
  # this is the implementation of the callback

  # which is the first argument of the bar function


Code is just in time compiled, and it feels like a scripting language from a developer’s perspective. You just point julia.exe at your source code and you’re away.

Another oddity is string concatenation:

"this is how you" * " add strings " * "together"

Anyway, any syntax looks odd until you get used to it.

There are a couple of ways (well there are lots actually) of importing modules. You can use using or import. This confused me until I read the documentation. using will take everything in the module, and add it to the scope. import namespaces everything with the modules name. I still prefer the require approach in node, but that’s just me.

Another things I like is that Julia uses libuv (and many other libraries) under the covers.

The Bad

Julia takes ages to start. I know it’s still work in progress, and improvements are being made to cache the compiled code, but it just feels too sluggish.

I have also found small stability problems, and find that my console can lock up when exiting a program.

The julia process locks the source files, stopping you from editing them while the program is running.

The string implementation makes me a bit sad, I seem to be spending too much time worrying about whether I’ve got a UTF8String or an ASCIIString.

The Ugly

The package system is not up to standard.

All packages seem to be installed globally (you can tell your program to search elsewhere) but I prefer my packages to be installed alongside my application. This makes it easer to copy my application from one machine to another.

I haven’t quite got my head around how the package versioning works, but it looks like you pick one version of a package for the machine. I think this is a poor choice, when compared to node.js, which is able to support multiple package versions in the same application.

The package repository is a GitHub repo. This on the face of it is a good idea. It’s a public database that you can take a local offline clone of. My problem with it is that it has gatekeepers (who (may) approve your contribution). I found some resistance to contributing. This can be a good thing, maintaining a high level of quality is important, but if there’s too much of a barrier to package entry, I’m not interested thanks.


I’ll stick with it and report back.