casting

问题 I am a beginner in Java. I came across a concept called Type Casting. I have the following snippet- class Demo { byte b; int a=257; double d= 323.142 b=(byte)a; System.out.println(b); b=(byte)d; System.out.println(b); } The output for the code is- 1 67 Can anybody explain me the outputs. Thanks in Advance! 回答1: The byte type is encoded on 8 bits, so it takes its values between -128 and 127. In your case, casting by byte is the same as computing a modulo and rounding to an int . Try the

问题 I'm probably missing something obvious here as this is basic functionality in other OOP languages, but I'm struggling with PHP way of doing this. I understand that PHP is not "true" OOP language, but still... What I'm after is casting an object instantiated as derived class to base class. Something along the lines of: class Some{} class SomeMock extends Some {} function GetSomeMock(){ $mock = new SomeMock(); return (Some)$mock; //Syntax error here } I've found some questions with strange

问题 I'm quite confused by this error: Cannot implicitly convert type 'System.Func<T,T,T> [c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.0\mscorlib.dll]' to 'System.Func<T,T,T> [c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.0\mscorlib.dll]' path\to\my\project\Operators.cs The types are identical, why is it even trying to do a cast? Here's the code: public static class Operators<T> { private static Func<T,T,T> _add = null; public

问题 I'd like to cast a numpy ndarray object of shape ( n ,) into one having shape ( n , 1). The best I've come up with is to roll my own _to_col function: def _to_col(a): return a.reshape((a.size, 1)) But it is hard for me to believe that such a ubiquitous operation is not already built into numpy's syntax. I figure that I just have not been able to hit upon the right Google search to find it. 回答1: I'd use the following: a[:,np.newaxis] An alternative (but perhaps slightly less clear) way to

问题 I'm looking at example abo3.c from Insecure Programming and I'm not grokking the casting in the example below. Could someone enlighten me? int main(int argv,char **argc) { extern system,puts; void (*fn)(char*)=(void(*)(char*))&system; char buf[256]; fn=(void(*)(char*))&puts; strcpy(buf,argc[1]); fn(argc[2]); exit(1); } So - what's with the casting for system and puts? They both return an int so why cast it to void? I'd really appreciate an explanation of the whole program to put it in

问题 Apple has the following method in the SKPhysicsBody class. /* Returns an array of all SKPhysicsBodies currently in contact with this one */ func allContactedBodies() -> [AnyObject]! I noticed it returns an array of AnyObject. So I read about how to deal with down casting AnyObject Here I want to loop through the allContactedBodies array of my physics body. The problem is, no matter what I try I just can't get things to work. I tried this first: for body in self.physicsBody.allContactedBodies(

问题 I want the datacontext of my listview to be binded to an observable collection. Right now I have: // CurrentEmploye = some employee Entities.DatabaseModel m = new Entities.DatabaseModel(); var q = from t in m.TimeSheet join emp in m.Employees on t.idEmployee equals emp.id where emp.id == CurrentEmploye.id select new { firstName = emp.firstName, lastName = emp.lastName, position = emp.position, clockInDate = t.clockInDate, clockOutDate = t.clockOutDate, }; listView1.DataContext = q; that code

问题 I have, struct S {} Along with, func y (x: S) -> AnyObject {} In Swift 2, is it possible to, within y(), return x My current code: struct S {let value: Int = 0} let x = S() func y(x: S) -> AnyObject {return x} Yields the following error: return expression of type 'S' does not conform to type 'AnyObject' Is there a way to mitigate this? 回答1: A Struct cannot conform to AnyObject . It can only conform to Any 来源： https://stackoverflow.com/questions/33921907/how-to-cast-a-struct-to-anyobject-in

问题 I have a view which needs to return type decimal for columns stored as float. I can cast each column to decimal as follows: , CAST(Field1 as decimal) Field1 The problem with this approach, is that decimal defaults to 18,0, which automatically rounds the float columns to 0. I would like to keep a precision of up to 12 decimal places. However, if I do this: , CAST(Field1 as decimal(12,12)) Field1 I get a runtime error: "Arithmetic overflow error converting float to data type numeric" the float

问题 In golang, a number in JSON message is always parsed into float64. In order to detect if it is actually integer, I am using reflect.TypeOf() to check its type. Unfortunately there is no constant that represents reflect.Type . intType := reflect.TypeOf(0) floatType := reflect.TypeOf(0.0) myType := reflect.TypeOf(myVar) if myType == intType { // do something } Is there more elegant solution instead of using 0 or 0.0 to get reflect.Type ? 回答1: You may also use the Value.Kind() or Type.Kind()