[josevalim]

It would be possible to have something like `Enum.map |> Enum.into`. You could also do `Stream.map |> Enum.into` if you don't want to traverse it multiple times (similar to Clojure's `into`). In fact:

    iex> Stream.unfold("hello", &String.next_codepoint/1) |> Enum.to_list
    ["h", "e", "l", "l", "o"]

The reasons we don't have first class support for this though are:

1. There are multiple ways you could traverse a string. By bytes, by codepoints or by graphemes. I don't think we should pick any of those as default. Ruby did that and to this day it is source of confusion (aggravated by the behavior change from 1.8 to 1.9)

2. Modifying strings like this would be horribly inefficient. Using split/join wouldn't be recommended also as you are generating a bunch of intermediate garbage to go from string -> string. The recommended way is to rely on pattern matching and Elixir's bit syntax as the compiler will be able to optimize most cases well.