Monadex bind operator


I am trying a new library called Monadex and in specific I am trying the Result Monad. The documentation mentions a function called Result.bind and I have made it work with the following code snippet:

defmodule TestMonadex do
  use Monad.Operators

  import Monad.Result

  def p1(x) do
    |> success()
    |> bind(&plus_1/1)

  defp plus_1(n), do: n + 1

And so far so good.


The problem arises when I try to use the bind operator. According to the docs, this operator is the same thing as the Result.bind function. Following this logic, the following code snippet should work:

defmodule TestMonadex do
  use Monad.Operators

  import Monad.Result

  def p2(x) do
    success(x) ->> (&plus_1/1) # This does not compile!

  defp plus_1(n), do: n + 1

Unfortunately, this is not compiling:

(SyntaxError) syntax error before: '>'

  │ (elixir 1.11.2) lib/kernel/parallel_compiler.ex:314: anonymous fn/4 in Kernel.ParallelCompiler.spawn_workers/7

an expression is always required on the right side of ->. Please provide a value after ->

At this point I strongly believe I am not understanding something from the docs or from the library.


What a I doing wrong?

The operator is ~>>, not ->>. It uses a tilde ~ instead of a dash. That code is parsed as

-> > (&plus_1/1)

Ie -> followed by the strictly greather than operator >, which is invalid.

So the documentation is wrong:

Or does it appear different in your browser ?

I still see a tilde, but the font choice may be a poor one and it’s easy to not spot the difference
It’s clearer looking at the source: MonadEx/operators.ex at master · rob-brown/MonadEx · GitHub
Or zooming:

Definitely an accessibility issue

Good point there, even the URL has a tilde.

Out of curiosity, what is your browser’s default font ?

The default one, it think it’s Arial since I’m on windows.
I do see the same as in your screenshot though, and the difference is barely noticeable.

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