equality

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 public class FunctionSet { public void doubleUp(int a) { System.out.println(a*2); } public void square

Possible Duplicate: php == vs === operator i have the following code fragment and it doesn't make sense to me why would NULL be evaluated in 3 different ways. Consider the variable $uploaded_filenames_array as UNKNOWN - we don't know whether it's still an array or a NULL. That's what we are trying to check. //----------------------------------------------- if (is_null($uploaded_filenames_array)){ echo "is_null"; } else{ echo "is_NOT_null"; } //----------------------------------------------- if ($uploaded_filenames_array == NULL){ echo "NULL stuff"; } else{ echo "not NULL stuff"; } //----------

I 'm integrating a geographic coordinate class from CodePlex to my personal "toolbox" library. This class uses float fields to store latitude and longitude. Since the class GeoCoordinate implements IEquatable<GeoCoordinate> , I habitually wrote the Equals method like so: public bool Equals(GeoCoordinate other) { if (other == null) { return false; } return this.latitude == other.latitude && this.longitude == other.longitude; } At this point I stopped and considered that I 'm comparing floating point variables for equality, which is generally a no-no. My thought process then went roughly as

I am running into an issue where I'm adding an instance to a set and then later testing to see whether or not that object exists in that set. I've overridden __eq__() but it doesn't get called during the inclusion test. Do I have to override __hash__() instead? If so, how would I implement __hash__() given that I need to hash the tuple, the list, and the dictionary? class DummyObj(object): def __init__(self, myTuple, myList, myDictionary=None): self.myTuple = myTuple self.myList = myList self.myDictionary = myDictionary def __eq__(self, other): return self.myTuple == other.myTuple and \ self

What does <=> in MySQL mean and do? The manual says it all: NULL-safe equal. This operator performs an equality comparison like the = operator, but returns 1 rather than NULL if both operands are NULL, and 0 rather than NULL if one operand is NULL. mysql> select NULL <=> NULL; +---------------+ | NULL <=> NULL | +---------------+ | 1 | +---------------+ 1 row in set (0.00 sec) mysql> select NULL = NULL; +-------------+ | NULL = NULL | +-------------+ | NULL | +-------------+ 1 row in set (0.00 sec) mysql> select NULL <=> 1; +------------+ | NULL <=> 1 | +------------+ | 0 | +------------+ 1

How do I deal with null fields in GetHashCode function? Module Module1 Sub Main() Dim c As New Contact Dim hash = c.GetHashCode End Sub Public Class Contact : Implements IEquatable(Of Contact) Public Name As String Public Address As String Public Overloads Function Equals(ByVal other As Contact) As Boolean _ Implements System.IEquatable(Of Contact).Equals Return Name = other.Name AndAlso Address = other.Address End Function Public Overrides Function Equals(ByVal obj As Object) As Boolean If ReferenceEquals(Me, obj) Then Return True If TypeOf obj Is Contact Then Return Equals(DirectCast(obj,

In Java the following code can return false: IntegerPlus o1 = new IntegerPlus(1000); IntegerPlus o2 = o1; boolean b1 = o1 == o2; boolean b2 = o1.Equals (o2); Is this also a problem in C#? Or does C# perform the == in a way where it will always be true even if objects get moved? ( I describe the Java issue in greater detail here. ) Alexei Levenkov No. In C#/.Net hash code is not involved into default implementation of == , != or Equals . If object is reference type and it is moved by GC there is nothing outside of this object that will impact default comparisons. Edit : unrelated details about

I have a (simplified) table that is structured like so: Table: ItemData PK | ItemID | StoreFK | Retail 1 | 100101 | 1 | 4.99 4 | 100101 | 2 | 4.99 7 | 100101 | 3 | 0.99 2 | 100102 | 1 | 6.99 5 | 100102 | 2 | 6.99 8 | 100102 | 3 | 6.99 3 | 100103 | 1 | 7.99 6 | 100103 | 2 | 8.99 9 | 100103 | 3 | 9.99 I would like to return all the items that have a different retail at one or more stores: Returns: ItemID 100101 100103 Item 100101 has a lower retail at store 3 then at store 1 & 2 it is returned. Item 100103 has a different retail at each store location so it is returned. Item 100102 has equality

How we could find max non-repeatable value in the array with a time ~O(N) I was trying to do it during huge time, but I found only ~O(2N): int solution(int[] A) { List<Integer> arr = new ArrayList<Integer>(); Set<Integer> set = new HashSet<Integer>(); int max = 0; for(int i = 0; i < A.length; i++) { if(!set.add(A[i])) arr.add(A[i]); } for(int i = 0; i < A.length; i++) { if (max < A[i] && !arr.contains(A[i])) max = A[i]; } return max; } Could we do it a little bit faster?! int A[] = {5, 5, 3, 2, 3, 1}; Map<Integer, Integer> map = new HashMap<>(); for(int i : A) { Integer count = map.get(i); //