Option<T>

This a type to represent the presence or absence of a T value. If T is null it would be transformed in None and, if not, will be returned as Some<T>.

Operators

Implicit Option<T> (T?)

Allows the client to set the T value to an Option.

Option<int> option = 1;
//Some<int> 1

Option<int> option = null;
//None

Implicit T

Allows the client to get the T value from an Option.

Option<int> option = 1;
Console.Write(option);
//1

Implicit bool

Allows the client to know if an Option is Some (true) or None (false).

Option<int> option = 1;
if(option) 
    Console.WriteLine("Some");
else
    Console.WriteLine("None");
//"Some"

Properties

IsSome

Indicates if an Option is Some, holding a T.

Option<int> option = 1;
Console.WriteLine(option.IsSome);
//true

IsNone

Indicates if an Option is Nome, holding no value.

Option<int> option = Option.None<int>();
Console.WriteLine(option.IsNome);
//true

Methods

Bind<TResult> (Func<T, Option<TResult>>)

Executes a given function over an Option, taking its T value, and returning an Option<TResult>.

Option<int> option = 1;
Option<string> bound = option.Bind((r) => r > 0 ? "Higher" : "Equal or Lower"));
//Some ("Higher")

Contains (T)

Verify if an Option is Some and it’s T is equal to a given T. If so returns true otherwise returns false.

Option<int> option1 = 1;
Option<int> option2 = Option.None<int>();
Console.Write(option1.Contains(option2));
//false

Count

Verify if an Option is Some. If so returns 1 otherwise returns 0.

Option<bool> option = true;
Console.Write(option.Count());
//1

DefaultValue (T)

Returns T from an Option if it is Some, otherwise returns the given default value.

var option = Option.None<int>();
Console.Write(option.DefaultValue(25));
//25

DefaultWith (Func<T>)

Returns T from an Option if it is Some, otherwise returns the result of the given function.

Option<int> option = Option.None<int>();
Console.Write(option.DefaultWith(() => 25));
//25

Exists (Func<T, bool>)

Verify if T matches a given predicate and returns true if so or false if not or Option is None.

Option<int> option = 1;
Console.Write(option.Exists((s) => s > 0));
//true

Filter (Func<Option<T>, bool>)

Return the Option itself if its None or the predicate is true, otherwise returns None.

Option<int> option = 1;
var result = option.Filter((o) => o > 0));
//Some (1)

Flaten (Option<Option<T>>)

Returns T of the inner Option instance if it is Some, otherwise None.

Option<Option<string>> Option.Some<Option<string>>("Option!");
Console.Write(option.Flaten());
//"Option!"

Fold (Func<TState, T, TState>, TState)

Updates and returns TState by the given function if Option is Some, otherwise returns TState

Option<int> option = 1;
Console.Write(option.Fold((s, t) => s + t), 10);
//11

FoldBack (Func<T, TState, TState>, TState)

As Fold but inverting T and TState as the given function parameters order.

Option<int> option = 1;
Console.Write(option.FoldBack((r, s) => s + r), 10);
//11

ForAll (Func<T, bool>)

Verifies if Option is None. If so returns true, otherwise applies the given function to T.

Option<int> option = 1;
Console.Write(option.ForAll((r) => r > 10));
//false

Get

Returns the T if Some or throws an exception if None.

Option<int> option = Option.None<int>;
Console.Write(option.Get());
//throws OptionException;

Iter (Action<T>)

Executes the given action if Option is Some.

Option<int> option = 1;
option.Iter(() => Console.Write("It's ok!"));
//"It's ok!"

Map (Func<T, Option<TResult>>)

Returns the Option itself if None or the result of the given function applied to T as an Option<TResult>.

Option<int> option = 1;
Console.Write(option.Map((r) => r > 0 ? true : false));
//true

Map2 (Func<Option<T>>, Func<T, T, Option<T>>)

Returns None if the Option itself and the first parameter are None, otherwise returns the result of the given function with the Option itself and the first parameter as an Option<TResult>.

Option<int> option1 = 1;
Option<int> option2 = 2;
Console.Write(option1.Map2((o1, o2) => o1 == o2 ? o1 : 0));
//0

Map3 (Func<Option<T>>, Func<Option<T>>, Func<T, T, T, Option<TResult>>)

Returns None if the Option itself and the first and second parameters are None, otherwise returns the result of the given function with the Option itself and the first and second parameters as an Option<TResult>.

Option<int> option1 = 1;
Option<int> option2 = 2;
Console.Write(option1.Map2((o1, o2) => o1 == o2 ? o1 : 0));
//0

Match (Action<T>, Action)

Executes the first action based on T if Option is Some or the second action if None.

Option<int> option = 1;
option.Match((t) => Console.Write(t)), () => Console.Write("None"));
//1

OrElse (Option<T>)

Returns the Option itself if Some or the first parameter.

var option = Option.None<T>();
option.OrElse(2);
//Some (2)

OrElseWith (Func<Option<T>>)

Returns the Option itself if Some or the result of the given function.

var option = Option.None<T>();
option.OrElseWith(() => 25));
//Some (25)

ToArray

Returns an array with T if Option is Some, otherwise an empty one.

Option<int> option = 1;
Console.Write(option.ToArray().Length);
//1

ToList

As ToArray but returns a generic list with T.

Option<int> option = 1;
Console.Write(option.ToList().Count);
//1

ToOption

Returns Some if T is not null, or a None if so.

var myString = "Option!";
var option = myString.ToOption();
//Some ("Option!")