back_pipe v0.1.1 BackPipe

A simple backwards pipe operator for Elixir via the ~> operator.

Via the ~>/2 macro, overloads the operator as the backwards pipe. This lets you pipe the output of preceding logic into the final argument position of the next function.

Examples

# Import the operator into your module
import BackPipe

# Calling `use` will work too if you want
use BackPipe

# Basic usage
iex> "hello world" ~> String.split()
["hello", "world"]

# We can chain too
"hello world"
~> String.split()
~> Enum.concat(["oh"])
|> Enum.join(" ")
# "oh hello world"

# More useful: dynamically creating a struct
defmodule Traveler do
  defstruct [:id, :name, :location]

  def new(kwl) do
    kwl
    |> Map.new()
    |> Map.put(:location, "Unknown")
    ~> struct(__MODULE__)
  end
end

iex> Traveler.new(id: 1, name: "Hal")
%Traveler{id: 1, location: "Unknown", name: "Hal"}

Why?

Why not!

But really, this is mostly an experiment. Elixir provides both a set of reserved operators that can be overloaded and a macro system to do so. Plus, the backwards pipe operator is not a novel concept. Some other functional languages like F#, have them, and this is a study of what it could look like in Elixir.

Also, it does feel useful for the small handful of cases where the final argument in a function is often the result of a chain (i.e. pipeline) of operations, like in the struct example above.

Link to this section Summary

Link to this section Functions

Link to this macro

lhs ~> rhs (macro)