For an exercism exercise I wanted to do multiplication with the pipe operator, and simply using * does not work, neither does (*).

Now, it turns out the arithmetic operations are functions part of the Kernel module, and you can also call them as an actual function with Kernel.*(2, 2), which is equal to writing 2 * 2.

This enables you do do arithmetic as part of the pipe operation, see:

def monthly_rate(hourly_rate, discount) do
  hourly_rate
  |> daily_rate
  |> apply_discount(discount)
  |> Kernel.*(22)
  |> ceil()
end

In Ruby, you have the --fail-fast flag, which stops running the test suite at the first failed test. Convenient to get shorter feedback loops, with a long running test suite.

In Elixir, you can achieve the same with:

mix test --max-failures 1

And then when a test fails, you fix it, and make sure that it works with:

mix test --failed

That makes for shorter feedback loops!

The following is what I use to setup Elixir on my machines, where I want to make sure that I can jump to all definitions of Elixir library functions.

First, I install asdf. I go the Homebrew and Fish route, but you can also do it from the source and use your shell of choice.

Before I install Erlang, I make sure to set the right flags, because I don’t want Java or build any GUI stuff:

KERL_BUILD_DOCS="yes"
KERL_CONFIGURE_OPTIONS="--disable-debug --without-javac --without-wx"

After that, I go to the asdf-erlang repository, check that I have all the build requirements and install Erlang with:

asdf plugin add erlang https://github.com/asdf-vm/asdf-erlang.git

# check available Erlang versions
asdf list all erlang

# install the latest version
asdf install erlang 26.2.4

# enable it globally
asdf global erlang 26.2.4

Now, let’s install Elixir. Go to the asdf-elixir repository, make sure you have unzip installed, and do the following.

asdf plugin-add elixir https://github.com/asdf-vm/asdf-elixir.git

# check all available versions
asdf list all elixir

# install the latest version, but! Install by source, so we can jump to the definition of Elixir functions
asdf install elixir ref:v1.16.2

# enable elixir globally
asdf global elixir ref:v1.16.2

Now, it says it in the comments, but the important difference is that I install Elixir by reference instead of the pre-compiled versions because I also like to be able to jump to definitions of Elixir library functions.