eulerfx

// for http://www.fssnip.net/d2

type Fold<'b> = Fold of f:('b -> obj -> 'b) * z:'b
  with
    static member inline ($) (Fold(_,z), HNil) = z
    static member inline ($) (Fold(f,z), HCons(a,xs)) = f (Fold(f,z) |*| xs) a


// use

eulerfx

/// An async observer.
type AsyncObserver<'a> = 'a option -> Async<unit>

module AsyncObserver =
    
    let inline post a (obs:AsyncObserver<'a>) = obs (Some a)

    let inline stop (obs:AsyncObserver<'a>) = obs None

    let contramap (f:'b -> 'a) (o:AsyncObserver<'a>) : AsyncObserver<'b> = 

eulerfx

<?xml version="1.0" encoding="utf-8"?>
<feed xmlns="http://www.w3.org/2005/Atom"> 
	<title>Example Feed</title>
	<subtitle>A subtitle.</subtitle>
	<link href="http://example.org/feed/" rel="self" />
	<id>urn:uuid:60a76c80-d399-11d9-b91C-0003939e0af6</id>
	<updated>2003-12-13T18:30:02Z</updated>
	<author>
		<name>John Doe</name>
		<email>johndoe@example.com</email>

eulerfx

public static Func<T> Retry(Func<T> original, int retryCount)
{
    return () =>
    {
        while (true)
        {
            try
            {
                return original();
            }

eulerfx

public interface IOrderRepository
{
  Order Get(string Id);
  IList<Order> GetMostRecent(string customerId, int max = 20);
  void Add(Order order);
  void Remove(string Id);
}

eulerfx

public class Order
{
  public string Id { get; private set; }
  public string Number { get; private set; }
  public string CustomerId { get; private set; }
  public DateTime Date { get; private set; }
  public ICollection<OrderLineItem> Items { get; private set; }
  public decimal ShippingCharge { get; private set; }
  public decimal TaxCharge { get; private set; }
  public decimal Total

eulerfx

public OrderReadModel
{
  public string Id { get; private set; }
  public string OrderNumber { get; private set; }
  public DateTime Date { get; private set; }
  public decimal Total { get; private set; }
} 

eulerfx

select top(@max) 
  Id,
  OrderNumber,
  Date,
  Total = o.TaxCharge + o.ShippingCharge + (select sum(i.Amount * i.Quantity) from OrderLineItems i where i.OrderId = o.Id)
from Orders o
where o.CustomerId = @customerId
order by o.Date desc

eulerfx

public class UserProfile
{
    public string Name { get; set; }
    // implementation omitted
    public bool IsValid { get; }
}

var profile = new UserProfile();
// must query to ascertain validity
if (!profile.IsValid)

eulerfx

public class UserProfile
{
    public UserProfile(string name)
    {
      this.Name = name;
    }

    public string Name
    {
      get { return _name; }