The document discusses various approaches to programming including functional programming, parallelism, concurrency, and refactoring object-oriented code. It provides examples of summing a list functionally and with recursion, as well as examples of sorting arrays, partitioning data into groups, and managing orders with an exposed model and authorization checks.

1. Почему
функциональное
программирование?
Сборная солянка

2. def sum(list):
result = 0
for element in list:
result = result + element
return result
sum' [] = 0
sum' (x:xs) = x + sum' xs

3. public static <E extends Comparable<? super E>> List<E> quickSort(List<E> arr) {
if (arr.size() <= 1)
return arr;
E pivot = arr.getFirst();
List<E> less = new LinkedList<E>();
List<E> pivotList = new LinkedList<E>();
List<E> more = new LinkedList<E>();
for (E i: arr) {
if (i.compareTo(pivot) < 0)
less.add(i);
else if (i.compareTo(pivot) > 0)
more.add(i);
else
pivotList.add(i);
}
less = quickSort(less);
more = quickSort(more);
less.addAll(pivotList);
less.addAll(more);
return less;
}

4. def qsort[T <% Ordered[T]](list:List[T]):List[T] = {
list match {
case Nil => Nil
case x::xs =>
val (before,after) = xs partition (_ < x)
qsort(before) ++ (x :: qsort(after))
}
}

5. sum(L) ->
lists:foldl(fun(X, Sum) -> X + Sum end, 0, L).

7. Параллелизм
Программа выполняется
быстрее в условиях
многоядерного окружения
Конкурентность
Неизбежное
взаимодействие
конкурентных потоков в
предметной области

8. var x = 0;
setTimeout(function () { x = x + 1; }, 0);
setTimeout(function () { x = x * 2; }, 0);
console.log(x);

10. $people = array();
$men = array();
$women = array();
foreach ($people as $person) {
array_push(($person->gender == 'male' ? $men : $women), $person)
}
val people: Array[Person]
val (men, women) = people partition (_.gender == "male")

11. ???
val people: Array[Person]
val (men, women) = people.par partition (_.gender == "male")

12. ???
val people: Array[Person]
val totalMoney = people.par map (_.money) reduce (_+_)

13. actor {
receive {
case people: Set[Person] =>
val (men, women) = people partition (_.gender == "male")
Cosmopolitan ! women
Playboy ! men
}
}

14. class OrderController < ApplicationController
before_filter :authenticate_user!
before_filter :load_order, only: [:edit, :update, :destroy]
before_filter :create_order_from_params, only: [:new, :create]
before_filter :authorize_user_on_order!, only: [:edit, :update, :destroy]
before_filter :update_order_from_params, only: [:update]
before_filter :render_if_save_error, only: [:create, :update]
def new; end
def edit; end
def create
redirect_to success_url
end
def update
redirect_to @order
end
def destroy
@order.destroy
redirect_to success_url
end
def load_order
@order = Order.find params[:id]
end
def create_order_from_params
@order = Order.new params[:order]
end
def authorize_user_on_order!
permission_denied! unless current_user.can_edit? @order
end
def update_order_from_params
@order.update_attributes
end
def render_if_save_error
unless @order.valid?
render 'error' and return false
end
end

15. class OrderController < ApplicationController
before_filter :authenticate_user!
def new
@order = order
end
def create
@order = refreshed_order
@order.save
respond_with(@order)
end
def edit
@order = order
end
def update
@order = refreshed_order
@order.save
respond_with(@order)
end
def destroy
@order = order
@order.destroy
respond_with(@order)
end
private
def order
params[:id] ? ensure_access! Order.find(params[:id]) : Order.new
end
def resfreshed_order
order.tap { |o| o.attributes = params[:order] }
end
def ensure_access!(order)
current_user.can_edit?(order) ? order : permission_denied!
end
end

16. class OrderController < ApplicationController
before_filter :authenticate_user!
helper_method :order
def new; end
def edit; end
def create
order.save
respond_with(order)
end
def update
order.save
respond_with(order)
end
def destroy
order.destroy
respond_with(order)
end
private
def order
@_order ||= refresh(params[:id] ? ensure_access! Order.find(params[:id]) : Order.new)
end
def resfresh(order)
order.tap { |o| o.attributes = params[:order] if params[:order] }
end
def ensure_access!(order)
current_user.can_edit?(order) ? order : permission_denied!
end
end

17. class OrderController < ApplicationController
before_filter :authenticate_user!
def new; end
def edit; end
def create
order.save
respond_with(order)
end
def update
order.save
respond_with(order)
end
def destroy
order.destroy
respond_with(order)
end
expose(:order) {
refresh(params[:id] ? ensure_access! Order.find(params[:id]) : Order.new)
}
private
def resfresh(order)
order.tap { |o| o.attributes = params[:order] if params[:order] }
end
def ensure_access!(order)
current_user.can_edit?(order) ? order : permission_denied!
end
end