defconstant - library for defining constants in your module

@jeg2

Really cool work, thank you!

Nice! For anyone super lazy here’s a simple example of using the defined 0-arity functions:

defmodule MyConstants do
  import Defconstant

  defconst the_answer, do: 42

  def my_func do
    the_answer() * 2 # returns 84
  end
end

I’ve also submitted a PR to add more docs and examples.

I was puzzled at first by the usefulness of this but after reading the code, I get it and it’s very cool.

I like the doc additions, @axelson. I feel that while getting an actual error over a “won’t match” warning you would get with def is quite useful, I see the bigger value prop of defconst to be that it avoids this problem, so perhaps calling that out as well would be good.

I also have an idea to provide comptime/const macro that would force compile time evaluation (quite it will be just wrapper on unquote) and once macro. That would allow to write in-function fragments that will have the same semantics as defconst and defonce.

Ah dang, my bad, I thought it was already doing this. The second part of my previous can be ignored.

Top notch. I think this would feel right at home In the standard library.

I have added support for private functions (haven’t released version 1.1.0 with that features yet). But it have come to me that there is one behaviour that may be problematic for some people, so I come here with question for anyone interested in this library:

https://github.com/hauleth/defconst/issues/3

I would like to hear your opinions on that issue.

FYI a long time ago I had created a similar library for Elixir called ex_const which also included support for enumerated values. There never was much interest, so I didn’t go much further.

I guess since the docs pushed to just use module attributes, it’s normal people would just use that, I try to follow conventions over libraries unless there is a clear gap in the std.
But your library is sound!