Do now for Tuesday the 21st of March. Converting a string into a dictionary by last names.

Main.elm

module Main exposing (..)

import Html exposing (Html, div, text)
import Dict exposing (Dict)

names : String -> Dict String (List String)
names str =
    str
        |> String.split ", "
        |> List.map (\name -> String.split " " name)
        |> List.foldl insertNames Dict.empty

insertNames : List String -> Dict String (List String) -> Dict String (List String)
insertNames names dict =
    Dict.update (names |> List.reverse |> first) (addOrUpdate (first names)) dict

addOrUpdate : String -> Maybe (List String) -> Maybe (List String)
addOrUpdate str value =
    case value of
        Just n ->
            Just (str :: n)

        Nothing ->
            Just [ str ]

first : List String -> String
first list =
    list
        |> List.head
        |> Maybe.withDefault "Not Given"

main : Html a
main =
    let
        foo = (names "George Washington, Adam West, Kanye West")
    in
        div []
            [ (text <| toString foo)
            , div [] [ text <| toString <| foo == Dict.fromList [ ( "Washington", [ "George" ] ), ( "West", [ "Kanye", "Adam" ] ) ] ]
            ]

names.rb

def names(str)
  Hash[str
     .split(", ")
     .map { |full_names| full_names.split(" ") }
     .group_by { |(first, last)| last }
     .map { |(last_name, full_names)| [last_name, full_names.map(&:first)] }]
end


expected = { "West" => ["Kanye", "Adam"], "Washington" => ["George"] }
actual   = names("George Washington, Kanye West, Adam West")
puts expected
puts actual
puts expected == actual