Learning OCaml

• Installation
• Conclusion

I have spent my entire career basically using two major languages; or at least language families. The first is the .NET languages. I started with VB.NET, moved to C#, and then ended up going back to VB.NET. I have spent more time than I would like to admit to dabbling in VBA, but honestly, I don’t really count that. Then I started a new job and picked up python. I have been using python professionally ever since. Is that all I know? Of course not. I have written a lot of bash and PowerShell. Again, I don’t really count those. No one, that I know of, gets paid to write bash for a living. I have spent free time learning Go and I learned C++ in college. Those languages are great, but they feel like they’re in the same “family.” I put that in quotes because a lot of people will want to quibble about me lumping .NET, python, Go, and C++ in a family. In a lot of ways they’re not, but they all “feel” about the same. They’re mostly procedural, object oriented, and most of that group also uses or borrows heavily from C’s syntax.

I want to teach myself something different. What are some “different” languages in my opinion? Scheme and Lisp immediately come to mind for me. While I have immense respect for both of them, and would like to, at some point, learn to write at least one of those two effectively, today isn’t that day. Instead I’m looking to go fully functional. So that brings me to OCaml.

Installation

I’m picky about how I install software. I spent two days worth of free time fighting with Gerbil Scheme to make it install cleanly (for my definition of clean). I eventually gave up and decided to skip learning Gerbil altogether.

Generally speaking, I followed the instructions laid out by the book Real World OCaml when setting up opam and ocaml. I did deviate a little to make sure everything was “tidy” when I finished which I will cover in detail here.

First, I went here and downloaded the bash script to install the binary distribution. If you just run it as they describe you can’t pass any options to the script.

curl -fsSLO https://raw.githubusercontent.com/ocaml/opam/master/shell/install.sh
chmox +x install.sh
./install.sh --no-backup --fresh

The script will ask where you want to install everything to, so don’t worry about not specifying that when you invoke it. I try to keep as much as possible in ~/.local so I chose ~/.local/bin. Assuming you have ~/.local/bin in your path, you should be able to run opam now and get the help menu.

opam

Now we get to the part where my OCD kicks in. I don’t want my home directory polluted with an opam directory. The next instruction listed in the book will create ~/opam for you and install everything there. But you can set an environment variable in your ~/.bashrc and opam will install everything there instead, so let’s do that.

export OPAMROOT="/home/steveno/.local/share/opam"

Now, going back to following the directions from the book, we initialize opam.

opam --init

Now, if you run that and you get this message about bwrap being not permitted, and it asking you if you want to disable sandboxing, and you’re running Ubuntu, this fix worked for me.

bwrap: loopback: Failed RTM_NEWADDR: Operation not permitted

sudo touch /etc/apparmor.d/bwrap

{
    echo "abi <abi/4.0>,"
    echo "include <tunables/global>"
    echo "" 
    echo "profile bwrap /usr/bin/bwrap flags=(unconfined) {"
    echo " userns,"
    echo "" 
    echo " # Site-specific additions and overrides. See local/README for details."
    echo " include if exists <local/bwrap>"
    echo "}"
} >> /etc/apparmor.d/bwrap

sudo systemctl reload apparmor.

Finally, opam init is going to ask you if you want it to setup your bash configuration for you or not. I picked yes the first time I did this, and now that I have it integrated into my bash configuration the way I want it, I pick no.

I went ahead and installed the recommended packages it talks about. I don’t really know what I am doing yet, so it seems like a safe bet for a learner.

opam install core core_bench utop

To finish off this post I, again, created the .ocamlinit file as directed.

{
    echo '#require "core.top";;'
    echo '#require "ppx_jane";;'
    echo 'open Base;;'
} >> ~/.ocamlinit

Conclusion

That should give you a nice working install of opam and ocaml. And, except for that init file at the end, your home directory should still be nice and tidy as well!