Since there's no usable documentation for this library I'll ask a question here.
I have a Cart which may have an Item in it. An Item has a Discount, which may be NoDiscount or PercentDiscount.
public record Cart(String id, Item item, int quantity)
public record Item(String sku, double price, int leftInStock, Discount discount)
sealed interface Discount permits NoDiscount, PercentDiscount
public record NoDiscount() implements Discount
public record PercentDiscount(double value) implements Discount
I have some Optics:
private static final Lens<Cart, Item> itemL = Lens.lens(Cart::item, (Item i) -> (Cart c) -> new Cart(c.id(), i, c.quantity()));
private static final Lens<Item, Discount> discountL = Lens.lens(Item::discount, d -> i -> new Item(i.sku(), i.price(), i.leftInStock(), d));
private static final Prism<Discount, Double> onlyPctDiscount
= Prism.prism(
d -> {
if(d instanceof PercentageOff) {
return Option.some(((PercentageOff) d).value());
}
else {
return Option.none();
}
},
PercentageOff::new
);This code recalulates the Item's Discount given a Cart:
itemL.composeLens(discountL).composePrism(onlyPctDiscount).modify(calculation).f(cart);
If I change the Cart to have a List of Item's, to recalculate the discount for each item in the cart I'm pretty sure I need to change that Prism to a Traversal.
How do I create a traversal for a list with any number of Items. From what I can make out FJ only allows Traversals for 2 to 6 items in a List.
Since there's no usable documentation for this library I'll ask a question here.
I have a
Cartwhich may have anItemin it. AnItemhas aDiscount, which may beNoDiscountorPercentDiscount.I have some Optics:
This code recalulates the
Item'sDiscountgiven aCart:If I change the
Cartto have aListofItem's, to recalculate the discount for each item in the cart I'm pretty sure I need to change thatPrismto aTraversal.How do I create a traversal for a list with any number of
Items. From what I can make out FJ only allowsTraversals for 2 to 6 items in aList.