Lets go shopping in Erlang

shop.erl

% shop.erl
-module(shop).
-export([cost/1]).

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

% shop1.erl
-module(shop1).
-export([total/1]).

total([ {What,N} | T]) -> shop:cost(What)*N + total(T);
total([]) -> 0.

% See the result for 
shop1:total([{oranges,5},{milk,3}] .

% First 5 * 5 + total([{milk,3}]
% Second 25 + 21 + total([]) 
% Third 25 + 21 + 0
% Result 46