ROTR

After reading about what Erlang has been used for, and about several of its pros and cons, I've decided to break out of my Python shell a bit and learn my first new programming language since 2002, when I was first introduced to Python. (Well, I've learned a bit more about things like JavaScript since then, but Python is the only one that I really dove into.)

It's also the first functional language I've learned, which is exciting, and is making me think about things a lot differently than I have before, even though I'm only 127 pages into Joe Armstrong's book.

I also like Emacs, in particular the variant that I use, Aquamacs.

The concept I just now learned about was the existence of escript, which lets you put a hash-bang line at the top of an erlang source file, make it executable, then run it as a script without using a wrapper script.

Out of the box, Emacs doesn't recognize that first line as an indicator that erlang-mode should be used.

Easy to fix. Just add a mode line in a comment as the second line in the file:

#!/usr/bin/env escript
%% -*- mode: erlang -*-

main([In]) ->
    X = list_to_integer(In),
    N = factorial(X),
    io:format("factorial ~w = ~w~n", [X, N]).

factorial(0) ->
    1;
factorial(N) ->
    N * factorial(N - 1).