C# IStructuralEquatable nerelerde kullanılıyor Aptallar için

C# IStructuralEquatable nerelerde kullanılıyor Aptallar için

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It's normally expected that if you implement IEquatable.Equals you will also override Object.Equals to be consistent. In this case how would you support both reference and structural equality?

In this case you don't want to change your class implementation so you don't wantoverride the Equals method. this will define a general way to compare objects in your application.

That is right! When we override Equals we must also override and implement GetHashCode. I am no HashCode expert, but in the same article from Sergey is a snippet of using a ValueTuple to simplify this entire call to 1 line of code just like our fancy ValueTuple Equality above.

IStructuralComparable arayüzü, çoğunlukla Array ve Tuple kabilinden muta bünyeları tarafından uygulanır. Bu done bünyeları, elemanlarının sıralamasını ve yapısını dikkate alarak karşılaştırma yapar.

It is used by the third example as an argument to the Equals(Object, IEqualityComparer) method of the IStructuralEquatable interface that tuples implement. It compares two Double or two Single values by using the equality operator. It passes values of any other type to the default equality comparer.

The generic tuple classes (Tuple, Tuple, Tuple, and so on) and the Array class provide explicit implementations of the IStructuralEquatable interface. By casting (in C#) or converting (in Visual Basic) the current instance of an array or tuple to an IStructuralEquatable interface value and providing your IEqualityComparer implementation kakım an argument to the Equals method, you gönül define a custom equality comparison for the array or collection.

After some more testing I found that any two arrays with the same first element have the same hash. I still think this is strange behavior.

Consider that there are only ~4.2 billion different hashcodes. Kişi you create more than this many different objects of the type on which GetHashCode is called? In this case it is C# IStructuralEquatable Kullanımı easy to see the answer is "yes". So GetHashCode is a sort of compressing projection onto a smaller seki - there are bound to be duplicates.

Reading through the excellent blog post by Sergey on struct equality performance he mentions that the default implementations are pretty slow and using boxing for each member. Additionally, he mentions that a memory comparison may hamiş give you the correct results in this super simple example:

If you read this entire post and are thinking wow that is a lot of code and steps to remember then do hamiş fear because Dustin told me and showed me that Visual Studio will generate all of this for you!!!!! Check this out:

Net on a certain platform, I'm compelled to issue the standard warning hamiş to rely on the values of hashcodes or how they are computed, since it is not guaranteed to be the same across updates or platforms.

IStructuralEquatable is used with arrays to determine whether the arrays are structurally equal. The StructuralEqualityComparer.Equals method is used for this purpose.

Default property. The second time, it passes the default equality comparer that is returned by the StructuralComparisons.StructuralEqualityComparer property. The third time, it passes the custom NanComparer object. As the output from the example shows, the first three method calls return true, whereas the fourth call returns false.

However, this is derece so great if you are using the struct in a dictionary birli my good friend Dustin mentioned to me because a Dictionary will always use the object version of Equals, which falls back to boxing :(