What does "|>" mean in elixir?

Question

I'm reading through some code elixir code on github and I see |> being used often. It does not appear in the list of operation on the documentation site. What does it mean?

i.e.

expires_at:    std["expires_in"] |> expires_at, 

Answer 1

This is the pipe operator. From the linked docs:

This operator introduces the expression on the left-hand side as the first argument to the function call on the right-hand side.

Examples

iex> [1, [2], 3] |> List.flatten()

[1, 2, 3]

The example above is the same as calling List.flatten([1, [2], 3]).

Answer 2

it gives you ability to avoid bad code like this:

orders = Order.get_orders(current_user) transactions = Transaction.make_transactions(orders) payments = Payment.make_payments(transaction, true) 

same code using pipeline operator:

current_user |> Order.get_orders |> Transaction.make_transactions |> Payment.make_payments(true) 

look at Payment.make_payments function, there is second bool parameter. The first parameter references the variable that is calling the pipe:

def make_payments(transactions, bool_parameter) do    //function  end 

when developing elixir application keep in mind that important parameters should be at first place, in future it will give you ability to use pipeline operator.

I hate this question when writing non elixir code: what should i name this variable? I waste lots of time on answer.