100 lines
3.9 KiB
C#
100 lines
3.9 KiB
C#
using System;
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using System.Linq;
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public static class Equality {
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// TODO: values returned by fieldAccessors should implement IEquatable.
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// T can be any supertype of the instances passed to the == operator.
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public static bool Operator(Object a, Object b) {
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if (Object.ReferenceEquals(a, b)) {
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return true;
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} else if (Object.ReferenceEquals(a, null)) {
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return Object.ReferenceEquals(b, null);
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} else if (Object.ReferenceEquals(b, null)) {
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return false;
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} else {
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return ((Object)a).Equals(b);
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}
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}
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// T must be the exact type of the receiver object whose
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// Object.Equals(Object other) method is invoking
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// Untyped(this, other).
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public static bool Untyped<T>(T a, Object b, Func<Object, T> cast, Func<T, int> hashCode, params Func<T, T, bool>[] comparers) {
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if (Object.ReferenceEquals(a, b)) {
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// Short path when the two references are the same.
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return true;
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} else if (Object.ReferenceEquals(a, null)) {
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return Object.ReferenceEquals(b, null);
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} else if (Object.ReferenceEquals(b, null)) {
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return false;
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} else {
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var castB = cast(b);
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if (Object.ReferenceEquals(castB, null)) {
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return false;
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} else {
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if (hashCode(a) != hashCode(castB)) {
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return false;
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} else {
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foreach (var comparer in comparers) {
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if (!comparer(a, castB)) {
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return false;
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} else {
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// continue.
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}
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}
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return true;
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}
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}
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}
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}
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public static bool Untyped<T>(T a, Object b, Func<Object, T> cast, Func<T, int> hashCode, params Func<T, Object>[] fieldAccessors)
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=> Untyped<T>(
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a,
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b,
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cast,
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hashCode,
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(aa, bb) =>
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fieldAccessors.All(
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accessor =>
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Equality.Operator(
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accessor(aa),
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accessor(bb))));
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// common method when there are no fields or comparers.
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public static bool Untyped<T>(T a, Object b, Func<Object, T> cast, Func<T, int> hashCode)
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=> Untyped<T>(a, b, cast, hashCode, (aa, bb) => true);
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// T must be the exact type of the receiver object whose
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// IEquatable<U>.Equals(U other) method is invoking
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// Equatable(this, other).
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public static bool Equatable<T>(T a, Object b) where T : IEquatable<T> {
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if (Object.ReferenceEquals(a, b)) {
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// Short path when the two references are the same.
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return true;
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} else if (Object.ReferenceEquals(a, null)) {
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return Object.ReferenceEquals(b, null);
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} else if (Object.ReferenceEquals(b, null)) {
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return false;
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} else {
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return ((Object)a).Equals(b);
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}
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}
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public static int HashCode(Object o1) => System.HashCode.Combine(o1);
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public static int HashCode(Object o1, Object o2) => System.HashCode.Combine(o1, o2);
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public static int HashCode(Object o1, Object o2, Object o3) => System.HashCode.Combine(o1, o2, o3);
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public static int HashCode(Object o1, Object o2, Object o3, Object o4) => System.HashCode.Combine(o1, o2, o3, o4);
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public static int HashCode(Object o1, Object o2, Object o3, Object o4, Object o5) => System.HashCode.Combine(o1, o2, o3, o4, o5);
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public static int HashCode(Object o1, Object o2, Object o3, Object o4, Object o5, Object o6) => System.HashCode.Combine(o1, o2, o3, o4, o5, o6);
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public static int HashCode(Object o1, Object o2, Object o3, Object o4, Object o5, Object o6, Object o7) => System.HashCode.Combine(o1, o2, o3, o4, o5, o6, o7);
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public static int HashCode(Object o1, Object o2, Object o3, Object o4, Object o5, Object o6, Object o7, Object o8) => System.HashCode.Combine(o1, o2, o3, o4, o5, o6, o7, o8);
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public static int HashCode(Object o1, Object o2, Object o3, Object o4, Object o5, Object o6, Object o7, Object o8, params Object[] objects) {
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var hash = System.HashCode.Combine(o1, o2, o3, o4, o5, o6, o7, o8);foreach (var o in objects) {
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hash = System.HashCode.Combine(hash, o);
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}
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return hash;
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}
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} |