elegance-syntax.el

class Order(customer: Customer) {
	option country=Countries.US
	items: Map<Item, Integer<Positive>>
	
	fn addItem(item: Item){
		option quantity: Integer<Positive>=1
		items[item] = quantity
	}
	
	fn getCount(item: Item): Int<Positive>?{
		items[item]
	}
	
	fn containsItem(item: Item): Bool {
		item in items
	}
	
	fn removeItem(item: Item){
		items.remove(item)
	}
	
}

adapt Order to Collection<Item>{
	add(item) -> addItem(item)
	remove(item) -> removeItem(item)
}

adapt Order to Map<Item, Integer<Positive>>{
	put(item, count) -> addItem(item, quantity=count)
	get(item) -> getCount(item)
	has(item) -> containsItem(item)
	remove(item) -> removeItem(item)
}

trait Positive for Int{
	Int.get() > 0
	Positive + Unsigned
	Unsigned + Positive
	Negative * Negative
	Positive * Positive
}

trait Zero for Int {
	Int.get() = 0
	Zero * Int
	Int * Zero
}

trait Unsigned for Int {
	Positive
	Zero
	Math.abs
}