Piping maps is trying to call the original function

Question

The following code is supposed to read a file and create an `Item` record for each line: ``` defmodule Ship do defrecord Item, product_code: 0, quantity: 0, destination: "" def load_data do File.read!("data") |> String.split |> Enum.map &(String.split &1, ",") |> Enum.map &(list_to_item &1) end defp list_to_item([pc, q, d | []]) do {parsed_q, _} = Integer.parse q Item.new product_code: pc, quantity: parsed_q, destination: d end end ``` There is a `data` file with the following content: ``` 1,100,London 1,30,Lisbon 3,2,Braga ``` The problem is, when I execute the load_data function, it looks like the last call to Enum.map is trying to call the parent function (load_data) recursively, and throwing a `BadArityError`. The output is as follows: ``` iex(1)> Ship.load_data ** (BadArityError) #Function<0.127338698/1 in Ship.load_data/0> with arity 1 called with 2 arguments ({:cont, []}, #Function<30.103209896/2 in Enum.map/2>) (elixir) lib/enum.ex:2000: Enumerable.Function.reduce/3 (elixir) l…

Accepted Answer

Your code is actually equivalent to this:

```
File.read!("data") 
|> String.split 
|> Enum.map (&(String.split &1, ",") |> Enum.map &(list_to_item &1))
```

You need more parentheses, because `|>` has a higher precedence than parenthesisless function application:

```
File.read!("data") 
|> String.split 
|> Enum.map(&(String.split &1, ","))
|> Enum.map(&(list_to_item &1))
```

This is an unfortunate flaw in the design of Elixir (and the sole reason I still prefer Erlang).

Piping maps is trying to call the original function

Solution

Problem