equality

问题 I have two variables: char charTime[] = "TIME"; char buf[] = "SOMETHINGELSE"; I want to check if these two are equal... using charTime == buf doesn't work. What should I use, and can someone explain why using == doesn't work? Would this action be different in C and C++? 回答1: char charTime[] = "TIME"; char buf[] = "SOMETHINGELSE"; C++ and C (remove std:: for C): bool equal = (std::strcmp(charTime, buf) == 0); But the true C++ way: std::string charTime = "TIME", buf = "SOMETHINGELSE"; bool

问题 This question already has answers here : Multiple string comparison with C# (7 answers) Closed last year . I have this piece of code: if (filter != RECENT && filter != TODAY && filter != WEEK && filter != MONTH && filter != ALLTIME) { filter = RECENT; } Note that filter is a string and it's compared against const string types. Is there any way to do this inline and have it be more readable? Doing it with the ternary operator doesn't make it much better since I still have to repeat filter !=

问题 The book says that "functions and closures are reference types". So, how do you find out if the references are equal? == and === don't work. func a() { } let å = a let b = å === å // Could not find an overload for === that accepts the supplied arguments Here is how the Catterwauls are dealing with this: MultiClosures & Equatable Closures tests 回答1: Chris Lattner wrote on the developer forums: This is a feature we intentionally do not want to support. There are a variety of things that will

问题 The book says that "functions and closures are reference types". So, how do you find out if the references are equal? == and === don't work. func a() { } let å = a let b = å === å // Could not find an overload for === that accepts the supplied arguments Here is how the Catterwauls are dealing with this: MultiClosures & Equatable Closures tests 回答1: Chris Lattner wrote on the developer forums: This is a feature we intentionally do not want to support. There are a variety of things that will

问题 According to the documentation of the == operator in MSDN, For reference types other than string, == returns true if its two operands refer to the same object. But, to be honest, I never check if two references are the same with == . I prefer using ReferenceEquals(obj1, obj2) and so do the default override of the Equals function. Therefore, in my projects, when the == operator is used on other types than string, equals to a bug. Is there a way to trigger a warning/error through Visual Studio

问题 Is there anyway to do a comparison between objects for equality generically without objects having an ID? I am trying to do a typical generic update, for which I have seen many examples of online, but they all usually look something like this: public void Update(TClass entity) { TClass oldEntity = _context.Set<TClass>().Find(entity.Id); foreach (var prop in typeof(TClass).GetProperties()) { prop.SetValue(oldEntity, prop.GetValue(entity, null), null); } } or something similar.The problem with

问题 On this page on MSDN they describe the SequenceEqual method of the Enumerable class. Halfway down the page it states: If you want to compare the actual data of the objects in the sequences instead of just comparing their references, you have to implement the IEqualityComparer generic interface in your class. The following code example shows how to implement this interface in a custom data type and provide GetHashCode and Equals methods. Then they show an example where they do not implement

问题 If I have a singly linked list in Haskell: data LL a = Empty | Node a (LL a) deriving (Show, Eq) I can easily implement methods to insert at the end and at the beginning. But what about inserting after or before a particular element? If I have a LL of Integer , can I make a distinction in Haskell between inserting 4 after a particular node containing a 1 , rather than the first 1 that it sees when processing the list? Node 1 (Node 2 (Node 3 (Node 1 Empty))) I'm curious how an insertAfter

问题 I'm implementing IEquatable in a custom class that has a List <T> as a property, like so: public class Person { public string FirstName { get; set; } public string LastName { get; set; } public List<string> Dislikes; public bool Equals(Person p) { if (p == null) { return false; } if (object.ReferenceEquals(this, p)) { return true; } return this.FirstName == p.FirstName && this.LastName == p.LastName && this.Dislikes == p.Dislikes; //or this.Dislikes.Equals(p.Dislikes) } public override int

问题 I'm trying to use heterogenous equality to prove statements involving this indexed datatype: data Counter : ℕ → Set where cut : (i j : ℕ) → Counter (suc i + j) I was able to write my proofs using Relation.Binary.HeterogenousEquality.≅-Reasoning , but only by assuming the following congruence property: Counter-cong : ∀ {n n′} {k : Counter n} {k′ : Counter n′} → {A : ℕ → Set} → (f : ∀{n} → Counter n → A n) → k ≅ k′ → f k ≅ f k′ Counter-cong f k≅k′ = {!!} However, I can't pattern match on k≅k′