CODEWITHSUNDEEP
c#.net
user8857966
user8857966

Reputation:

One Variable, Many Values?

This may sound like an odd question, and I have a feeling that the short answer is 'No'.

However, is there any way a variable could take more than one value, based on Boolean operators? For example:

//Current implementation
string Variable1 = "A";
string Variable2 = "B";
string Variable3 = "C";

//Sought after implementation
string Variable = "":
Variable = "A" || Variable = "B" || Variable = "C";

This doesn't look like it could be feasible, especially since Boolean operators can't be applied to string types, because, well... They're not Boolean.

Upvotes: 1

Views: 255

Answers (2)

Eric Lippert
Eric Lippert

Reputation: 660128

However, is there any way a variable could take more than one value, based on Boolean operators?

Sure! Let's implement it. We'll use the ImmutableHashSet<T> type from System.Collections.Immutable.

struct MySet<T>
{
    public readonly static MySet<T> Empty = default(MySet<T>);
    private ImmutableHashSet<T> items;
    private MySet(ImmutableHashSet<T> items) => this.items = items;
    public ImmutableHashSet<T> Items => this.items ?? ImmutableHashSet<T>.Empty;
    public MySet<T> Add(T item) => new MySet<T>(this.Items.Add(item));
    public static MySet<T> operator |(T item, MySet<T> items) => items.Add(item);
    public static MySet<T> operator |(MySet<T> items, T item) => items.Add(item);
    public static MySet<T> operator |(MySet<T> x, MySet<T> y) => new MySet<T>(x.Items.Union(y.Items));
    public static MySet<T> operator &(MySet<T> items, T item) => new MySet<T>(items.Items.Contains(item) ? ImmutableHashSet<T>.Empty.Add(item) : ImmutableHashSet<T>.Empty);
    public static MySet<T> operator &(T item, MySet<T> items) => new MySet<T>(items.Items.Contains(item) ? ImmutableHashSet<T>.Empty.Add(item) : ImmutableHashSet<T>.Empty);
    public static MySet<T> operator &(MySet<T> x, MySet<T> y) => new MySet<T>(x.Items.Intersect(y.Items));
}

Now we can create a variable that contains multiple values of any type, and obeys the laws of | and &:

    var items1 = MySet<String>.Empty | "Hello" | "Goodbye" | "Whatever";
    var items2 = MySet<String>.Empty | "Goodbye" | "Hello" | "Blah";
    var items3 = items1 & items2;
    var items4 = items1 | items2;
    Console.WriteLine(String.Join(" ", items3.Items)); // "Hello Goodbye"
    Console.WriteLine(String.Join(" ", items4.Items)); // "Hello Goodbye Whatever Blah"

Upvotes: 5

Robert Levy
Robert Levy

Reputation: 29073

Define an enum with the [Flags] attribute.

Reference: What does the [Flags] Enum Attribute mean in C#?

[Flags]
public enum PossibleValues { A = 1, B = 2, C = 4 }

var foo = PossibleValues.A | PossibleValues.B | PossibleValues.C;

Upvotes: 4

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