shop.erl

%% erlang pattern matching and list comprehension vs clojure destructure and hof
-module(shop).
-export([total/1]).

cost(oranges) -> 5;
cost(newspaper) -> 8;
cost(apples) -> 2;
cost(pears) -> 9;
cost(milk) -> 7.

sum([H | T]) -> H + sum(T);
sum([]) -> 0.

total(Items) ->
  sum([cost(A) * B || {A, B} <- Items]).

(def m {:orange {:quantity 4, :price 3}, :apple {:quantity 3, :price 2}})

(letfn [(per-count [item]
          (let [{:keys [quantity price]} (val item)]
            (* quantity price)))]
  (reduce + (map per-count m)))