83 lines
1.4 KiB
C#
83 lines
1.4 KiB
C#
interface ICovariant<out T>
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{
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T Foo { get; }
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}
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interface IContravariant<in T>
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{
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int Bar (T bar);
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}
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interface IBothVariants <out T1, in T2> : ICovariant<T1>, IContravariant<T2>
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{
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}
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interface IInvariant <T> : ICovariant<T>, IContravariant<T>
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{
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}
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class BothVariants <T1, T2> : IBothVariants <T1, T2>
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{
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public BothVariants (T1 foo)
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{
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Foo = foo;
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}
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public T1 Foo { get; private set; }
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public int Bar (T2 bar)
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{
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return bar.GetHashCode () ^ Foo.GetHashCode ();
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}
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}
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class Invariant <T> : IInvariant<T> where T : new()
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{
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public T Foo { get { return new T (); } }
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public int Bar (T bar)
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{
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return bar.GetHashCode ();
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}
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}
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class A
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{
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public virtual string Fruit { get { return "Apple"; } }
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}
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class B : A
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{
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public override string Fruit { get { return "Banana"; } }
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}
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class C : B
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{
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public override string Fruit { get { return "Carrot which I know is not a fruit but you better shut up about it before I cut you"; } }
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}
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public class Test
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{
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public static int Main ()
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{
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var b = new B ();
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var c = new C ();
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IBothVariants<A, C> both = new BothVariants<B,B> (b);
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if (both.Bar (c) != (b.GetHashCode () ^ c.GetHashCode ()))
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return 1;
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IInvariant<B> neither = new Invariant<B> ();
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ICovariant<A> co = neither;
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if (co.Foo.Fruit != "Banana")
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return 2;
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IContravariant<C> contra = neither;
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if (contra.Bar (c) != c.GetHashCode ())
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return 3;
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return 0;
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}
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}
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