View Source Pipes

Elixir makes data transformation extremely easy because you can pass the result of one function into the next by using the pipe |> operator:

add = fn a, b -> a + b end
mult = fn a, b -> a * b end

2
|> add.(3)
|> mult.(5)
|> IO.inspect(label: "Result")

Result: 25

then/2

A pipe always passes the result of a function into the next one as the first argument. You can use then/2 if you want to change the argument position or modify the result before passing it into the next function.

add = fn a, b -> a + b end
mult = fn a, b -> a * b end

2
|> add.(3)
|> then(fn result ->
  result = result * 2
  mult.(1024, result)
end)
|> IO.inspect(label: "Result")

Result: 10240

tap/2

The tap/2 helper allows you to 'tap into' a pipe without modifying its current value. It's useful for executing synchronous side effects without changing the value.

add = fn a, b -> a + b end
mult = fn a, b -> a * b end

2
|> add.(3)
|> tap(fn result ->
  IO.inspect(result, label: "Current")
  result * 2 # <- The result of this equation is ignored.
end)
|> mult.(5)
|> IO.inspect(label: "Result")

Current: 5
Result: 25