Elixir

Elixir was created by José Valim and first released in 2012. It runs on the Erlang virtual machine, here Erlang/OTP 27, which Ericsson built in the 1980s for telephone switches that had to keep running for years. Elixir gives that machine a friendlier syntax and keeps its strengths: millions of lightweight processes, and systems that restart the parts that fail. Discord’s chat servers and the Phoenix web framework are built on it.

Elixir is functional, and its data never changes in place. A function takes values and returns new ones, and the pipe operator, |>, chains them: path |> File.read!() |> String.split("\n"). Pattern matching takes values apart, as in [header | rows] = lines. Elixir can call any Erlang library directly, so the square root is :math.sqrt. Packages from Hex, Elixir’s package manager, aren’t installed here, including Nx, its numerical library.

Quirks

• / always gives a float, so 10 / 2 is 5.0. div(-7, 2) is −3, rounding toward zero, while Integer.floor_div(-7, 2) is −4.
• 1 == 1.0 is true, but 1 === 1.0 is false.
• String.to_float("12") raises an error because there’s no decimal point. Float.parse("12") gives {12.0, ""}.
• = matches rather than assigns. [header | rows] = lines takes the first line off, and a variable can be bound again: after x = 1 and x = 2, x is 2.
• 0 is true. Only nil and false are false.
• Matching the pattern 0.0 draws a warning since Erlang/OTP 27, because it no longer matches -0.0, so here it fails the run. x == 0 compares by value instead: 0.0 == 0 is true.
• A function with a missing clause compiles without a warning. With no clause for {:leaf, _}, the program runs until it meets a leaf, then stops with a FunctionClauseError.
• Enum.at([1, 2, 3], 5) gives nil, not an error.
• Enum.zip stops at the shorter list: zipping [1, 2, 3] with [:a, :b] gives two pairs.
• Elixir has no --warnings-as-errors for scripts, so the run script fails the run if any warning appears, such as an unused variable.

git clone https://github.com/qnixon/dswithx.git
cd dswithx
python3 harness/run_tests.py --language elixir