casting

问题 I'm using PHP 7.2.12 I come across following statement from the Type Casting section of PHP Manual : (binary) casting and b prefix forward support was added in PHP 5.2.1. Note that the (binary) cast is essential the same as (string), but it should not be relied upon. I didn't understand the above text thoroughly. Someone please explain to me with good explanation. I studied the following code examples given in PHP Manual on the same page : <?php $binary = (binary) $string; var_dump($binary);

问题 this is kind of a follow up question from this: Rust dynamic cast trait object between different taits The solution provided there works really well when we use references for trait objects. This time I was trying to do the same with Rc pointers. For example I have a super trait named TraitAB and 2 traits named TraitA and TraitB So when I first create a trait object of type TraitAB instead of using a Box , now I use an Rc pointer. I need a variable of type TraitA to be a reference of ab Here

问题 I have a set of business logic classes that inherit from a chain of abstract classes. I also have a set of business data classes that inherit from their own chain of abstract classes. In both cases my derived class (C) inherits from an abstract class (B), which itself inherits from an abstract class (A). (Therefore, C : B and B : A). In isolation, my chain of logic classes behave as expected. Method calls use the correct base or overridden implementations. The same goes for my data classes

问题 I'm currently converting and casting from Class to Class2 using the implicit operator. But what I want to do is, that, whenever I refer to foo (Class<Class2>) , I'd like for Goo(Class) to be returned so that I can access the public Properties of it directly, without having to cast it first into a new variable. In other words, I want that when I access Class<Class> , I'd like Goo to be returned. I'm aware I might have not been able to explain properly so feel free to ask in the comment section

问题 I asked a still unanswered question that will shed more light on this question. Why can't I do this... _wizardDialog.UIRoot.Controls.Clear() _wizardDialog.UIRoot.Controls.Add(TryCast(wizardUserControl, wizardUserControl.GetType)) Why does using GetType in this way fail. The argument for try cast are object and type. Since wizardUserControl.GetType returns a type how come this is not legal. Visual Studio is complaining wizardUserControl.GetType is not defined. The bottom line is how can I get

问题 I am making a game that involves a Game Center leaderboard. I want to make a custom leaderboard UI rather than using the default interface. I am trying to convert the values stored in a Game Center leaderboard into a string so that I may display them using an SKLabelNode. However, I get an error saying that: Cannot invoke initializer for type 'String' with an argument list of type '(Int64?)' I am accessing the Game Center scores using leaderboard.scores[i].value When I use the String

问题 If I have an object reference that references a byte? , short? or int? , is there a way to unconditionally cast or convert that object reference to int? without writing separate code for each case? For example: byte? aByte = 42; // .. or aByte = null object anObject = aByte; //... var anInt = (int?)anObject //As expected, doesn't work 回答1: I'd use Convert.ToInt32(object): object o = ...; // Boxing... int? x = o == null ? (int?) null : Convert.ToInt32(o); Note that when you box an int? , short

问题 As it's shown in the following code, I can call a non-static member function A::f without instantiating an object of the class. This is only possible when the function is not bound to any other member. For example, I cannot call A::g in a similar fashion. It seems to me that the call to A::f as shown in the code below behaves like calling a static member function. Is such a conclusion correct? How can this behavior be justified? #include <iostream> using namespace std; struct A { void f() {

问题 I tried using the reshape package to reshape a dataframe I got, but when using it, numbers in the dataframe are changed which should not be. The dataframe contains several variables as well as multiple times these variables have been measured, for each person there are 6 rows, that is 6 times that person has been measured. Now I want to reshape the dataframe so there is only one row for each person instead of 6, that means every variable should be there 6 times (once for every measurement),

问题 #include <stdio.h> #include <stdlib.h> #include <string.h> #include <assert.h> static int cmpstringp(const void *p1, const void *p2) { /* The actual arguments to this function are "pointers to pointers to char", but strcmp(3) arguments are "pointers to char", hence the following cast plus dereference */ return strcmp(* (char * const *) p1, * (char * const *) p2); } int main(int argc, char *argv[]) { int j; assert(argc > 1); qsort(&argv[1], argc - 1, sizeof(argv[1]), cmpstringp); for (j = 1; j