constants

问题 I am attempting to bind a WPF textbox's Maxlength property to a known constant deep within a class. I am using c#. The class has a structure not too dissimilar to the following: namespace Blah { public partial class One { public partial class Two { public string MyBindingValue { get; set; } public static class MetaData { public static class Sizes { public const int Length1 = 10; public const int Length2 = 20; } } } } } Yes it is deeply nested, but unfortunately in this instance I can't move

问题 I am reviewing some code and I ran across some code I am unfamiliar with. After some searching I could not come up of any example of why this is done or the benefit of this declaration. myClass const * const myPtr = myClass->getPointer(); Is this a declaration of a const pointer or something entirely different? 回答1: It means " myPtr is a const pointer to a const myClass ". It means that you can neither modify what the pointer is pointing at through this pointer nor can you make the pointer

问题 I am reviewing some code and I ran across some code I am unfamiliar with. After some searching I could not come up of any example of why this is done or the benefit of this declaration. myClass const * const myPtr = myClass->getPointer(); Is this a declaration of a const pointer or something entirely different? 回答1: It means " myPtr is a const pointer to a const myClass ". It means that you can neither modify what the pointer is pointing at through this pointer nor can you make the pointer

问题 Hello android developers, I am developing a simple game for Android in Eclipse using OpenGLES 1.0. I am using Samsung Galaxy S2 Android(2.3) as a device for development. And I have a question about dual core and making frame rate constant. So I have managed creating GLSurfaceView and override onDrawFrame() function where I call LogicUpdate(deltatime) function and Render() function. Yes, all in single thread for now. The problem I am getting is with dual core. If I disable dual core by going

问题 Note: I'm not talking about preventing the rebinding of a variable. I'm talking about preventing the modification of the memory that the variable refers to, and of any memory that can be reached from there by following the nested containers. I have a large data structure, and I want to expose it to other modules, on a read-only basis. The only way to do that in Python is to deep-copy the particular pieces I'd like to expose - prohibitively expensive in my case. I am sure this is a very common

问题 In C you can define constants like this #define NUMBER 9 so that wherever NUMBER appears in the program it is replaced with 9. But Visual C# doesn't do this. How is it done? 回答1: public const int NUMBER = 9; You'd need to put it in a class somewhere, and the usage would be ClassName.NUMBER 回答2: You can't do this in C#. Use a const int instead. 回答3: static class Constants { public const int MIN_LENGTH = 5; public const int MIN_WIDTH = 5; public const int MIN_HEIGHT = 6; } // elsewhere public

问题 In the below code: final int a; a=2; byte b=a; // error: possible loss of precision Why do I get this error? Isn't a final variable compile time constant expression and hence implicitly narrowed to byte during the assignment? In other words isn't the above code equivalent to: final int a=2; byte b=a; 回答1: The compiler isn't that smart. We can tell that the value will always be 2. But what if we had something like this? class ABC{ final int a; public ABC(){ if(Math.random() < .5){ a = 2; }

问题 In the below code: final int a; a=2; byte b=a; // error: possible loss of precision Why do I get this error? Isn't a final variable compile time constant expression and hence implicitly narrowed to byte during the assignment? In other words isn't the above code equivalent to: final int a=2; byte b=a; 回答1: The compiler isn't that smart. We can tell that the value will always be 2. But what if we had something like this? class ABC{ final int a; public ABC(){ if(Math.random() < .5){ a = 2; }

问题 I want a header file with a non-integral constant in it, e.g. a class. Note the constant does not need to be a compile-time constant. static const std::string Ten = "10"; This compiles but is undesirable as each compilation unit now has its own copy of Ten. const std::string Ten = "10"; This will compile but will fail with a linker error for multiply defined Ten. constexpr std::string Ten = "10"s; This would work but only if the strings constructor was constexpr as well. It will be but I can

问题 I have recently read about the const keyword, and I'm so confused! I can't find any difference between const and the val keyword, I mean we can use both of them to make an immutable variable, is there anything else that I'm missing? 回答1: const s are compile time constants. Meaning that their value has to be assigned during compile time, unlike val s, where it can be done at runtime. This means, that const s can never be assigned to a function or any class constructor, but only to a String or