rob-brown / MonadEx

Upgrade your pipelines with monads.
MIT License
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Bind operator question #11

Closed Fl4m3Ph03n1x closed 3 years ago

Fl4m3Ph03n1x commented 3 years ago

Background

I am trying this library 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
    x
    |> success()
    |> bind(&plus_1/1)
  end

  defp plus_1(n), do: n + 1
end

And so far so good.

Problem

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!
  end

  defp plus_1(n), do: n + 1
end

Unfortunately, this is not compiling:

(SyntaxError) syntax error before: '>'

Stacktrace:
  │ (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.

Question

What a I doing wrong?

rob-brown commented 3 years ago

The operator you're looking for is ~>>. It's a tilde instead of a hyphen. Otherwise it's ambiguous with the -> operator.

Fl4m3Ph03n1x commented 3 years ago

So the documentation is incorrect:

Capture

Or is it displayed differently in your browser?

Fl4m3Ph03n1x commented 3 years ago

After a closer look I have realized that my browser's zoom level, together with my font made the docs harder to read. Everything is correct.

Thank you for answer and I apologize for taking your time. Closing ticket.