equality

Actionscript Date Comparison

由 泄露秘密 提交于 2019-12-06 23:07:06
问题 In my Actionscript code I have two dates: var date1:Date = new Date(2011,1,1); var date2:Date = new Date(2011,1,1); This doesn't work: var equal:Boolean = date1 == date2; From reading I've found that this is a working alternative since it just gets the number of milliseconds from a standard point in time. var equal:Boolean = date1.getTime() == date2.getTime(); So my questions are: Why doesn't the normal equality operator work on Dates in actionscript? ">" as well as "<" operators seem to work

difference between is_null “== NULL” and “=== NULL” in PHP [duplicate]

由 怎甘沉沦 提交于 2019-12-06 19:27:15
问题 This question already exists : Closed 7 years ago . 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"; }

How to implement __eq__ for set inclusion test?

由 雨燕双飞 提交于 2019-12-06 19:21:09
问题 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

Why has Scala no type-safe equals method?

由 匆匆过客 提交于 2019-12-06 19:10:34
问题 Since the inventors highlight Scala 's type-safety I don't understand the absence of an equals method on objects (at least from case classes ) that allows to check the equality only on objects with same type. I'd wish a method === that implement this behavior per default. Of course its necessary for Java interoperability to have a method that works with Any type but in many cases I want to check only the equality between objects of same type. Why do I need it? For example I have two case

What does “<=>” in MySQL mean?

由 蹲街弑〆低调 提交于 2019-12-06 17:11:21
问题 What does <=> in MySQL mean and do? 回答1: 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

Tuple == Confusion

由 情到浓时终转凉″ 提交于 2019-12-06 17:11:04
问题 Suppose I define two tuples: Tuple<float, float, float, float> tuple1 = new Tuple<float, float, float, float>(1.0f, 2.0f, 3.0f, 4.0f); Tuple<float, float, float, float> tuple2 = new Tuple<float, float, float, float>(1.0f, 2.0f, 3.0f, 4.0f); If I try to compare the tuples, I get different results bool result1 = (tuple1 == tuple2); // FALSE bool result2 = tuple1.Equals(tuple2); // TRUE I would expect for both calls to return true. What exactly is == comparing? 回答1: For Tuple, the == is

GetHashCode on null fields?

由 谁说胖子不能爱 提交于 2019-12-06 17:01:13
问题 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

Strange compile errors in equality: (No method 'equals(Any?): Boolean' available)

由 孤者浪人 提交于 2019-12-06 16:14:43
The following code fun main(args: Array<String>) { val a = listOf('A', Pair('X', 'Y')) println(a[0] == 'B') } throws compile errors: Error:(4, 17) Unresolved reference: == Error:(4, 17) No method 'equals(Any?): Boolean' available as in the screenshot: Why do these compile errors occur? EDIT 1 : It seems it is not related with a when expression. EDIT 2 : Code snippet (Press the "run" button on the top right to compile) I need to cast manually to avoid the compile error. Using a smart cast also does not work. (Or val a: List<Any> = listOf('A', Pair('X', 'Y')) works) Lior Bar-On This is a tricky

How does an equal to expression work in a printf placeholder? [duplicate]

由 只谈情不闲聊 提交于 2019-12-06 15:13:37
This question already has answers here : Why are these constructs using pre and post-increment undefined behavior? (14 answers) Closed last year . I have the following code snippet: main( ) { int k = 35 ; printf ( "\n%d %d %d", k == 35, k = 50, k > 40 ) ; } which produces the following output 0 50 0 I'm not sure I understand how the first value of the printf comes to 0 . When the value of k is compared with 35 , it should ideally return (and thus print) 1, but how is it printing zero? The other two values that are produced- 50 and 0 are all right, because in the second value, the value of k is

Comparing Similar Columns for Equality

由 喜夏-厌秋 提交于 2019-12-06 13:00:34
问题 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.
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