equality

问题 This question already has answers here : Is there a way to compare lambdas? (3 answers) Closed 4 years ago . I am not sure how I can be sure about equality/immutability of functional interface. I guess there might be no way to assure equality when I use this syntactic sugar in java 8, please let me know any hint if you have any. I made a short code snippet for my question. public interface Element { void doSomething(int a); } and I've tried to add instance of this interface in functional way

问题 I am writing this neat class implementing IEqualityComparer, so that I can just pass any anonymous type to it (or actually any type with properties) and it will automatically compare the types by comparing the property values of the types. public class CompareProperty<T> : IEqualityComparer<T> { private Type type; private PropertyInfo propInfo; private string _fieldName; public string fieldName { get; set; } public CompareProperty(string fieldName) { this.fieldName = fieldName; } public bool

问题 I have made heavy use of case classes in my code, replying on the underlying equality definitions of case class to behave correctly. Then now I found that I need to add another field member to a case class. So if I add a var field member in case class, will it mess up the equality attributes for the case class? If 1 is yes, then what if I just change the var field value once, after that, no any reassignment will happen, before the case class goes into any collections or do equality comparison

问题 Is there a tool or library to find duplicate entries in a Collection according to specific criteria that can be implemented? To make myself clear: I want to compare the entries to each other according to specific criteria. So I think a Predicate returning just true or false isn't enough. I can't use equals . 回答1: It depends on the semantic of the criterion: If your criterion is always the same for a given class, and is inherent to the underlying concept , you should just implement equals and

问题 How can I compare if two json structures are the same in scala? For example, if I have: { resultCount: 1, results: [ { artistId: 331764459, collectionId: 780609005 } ] } and { results: [ { collectionId: 780609005, artistId: 331764459 } ], resultCount: 1 } They should be considered equal 回答1: You should be able to simply do json1 == json2 , if the json libraries are written correctly. Is that not working for you? This is with spray-json, although I would expect the same from every json library

问题 How to static_assert a template type is EqualityComparable concept in C++11? 回答1: You could use the following type trait: #include <type_traits> template<typename T, typename = void> struct is_equality_comparable : std::false_type { }; template<typename T> struct is_equality_comparable<T, typename std::enable_if< true, decltype(std::declval<T&>() == std::declval<T&>(), (void)0) >::type > : std::true_type { }; Which you would test this way: struct X { }; struct Y { }; bool operator == (X const

问题 After reading a related question about using slices in maps, I became curious about equality in Go. I know it's possible to override the equals method of a Java Object . Is there a similar way to define how Go checks user defined types/structs for equality? If so, there would be a workaround for the issue referenced above. I thought using interface{} values might offer a solution but I received the error message panic: runtime error: hash of unhashable type []int . 回答1: Go supports equality

问题 Looking at Go standard library, there's a ConstantTimeByteEq function that looks like this: func ConstantTimeByteEq(x, y uint8) int { z := ^(x ^ y) z &= z >> 4 z &= z >> 2 z &= z >> 1 return int(z) } Now, I understand the need for constant time string (array, etc.) comparison, as a regular algorithm could short-circuit after the first unequal element. But in this case, isn't a regular comparison of two fixed-sized integers a constant time operation at the CPU level already? 回答1: Not

问题 This question already has answers here : Closed 8 years ago . Possible Duplicate: Determine if two binary trees are equal Got an interview yesterday, a question got me, here it is: Description There are 2 binary trees , check if they are equal. They are equal if and only if tree1->child == tree2->child , and one tree's left and right children can be swapped with each other . For example: 5 6 / \ / \ they are equal. 1 2 2 1 5 6 / \ / \ they are equal. 1 2 2 1 / \ / / 3 4 4 3 Any ideas are

问题 I've got some code that relies on comparing two NSIndexPaths and executing different code based on their equality or lack thereof (using -isEqual). Most of the time it works properly, but sometimes it doesn't. I've used the debugger console to test the two indexpaths during code execution, and they look identical to me. Here's the code: - (BOOL)selectedStreetIsSameAsLastSelectedStreet { return [self.indexPathOfSelectedStreet isEqual:self.previousObject.indexPathOfSelectedStreet]; } Here's the