constants

问题 I'm using a well known template to allow binary constants template< unsigned long long N > struct binary { enum { value = (N % 10) + 2 * binary< N / 10 > :: value } ; }; template<> struct binary< 0 > { enum { value = 0 } ; }; So you can do something like binary<101011011>::value. Unfortunately this has a limit of 20 digits for a unsigned long long. Does anyone have a better solution? 回答1: Does this work if you have a leading zero on your binary value? A leading zero makes the constant octal

问题 So, I have an assembly function, which is called in C. It compiles and gives me no warnings, but when I try to run it, it gives me a segmentation fault. I think it's because I can't move a constant into a register, but to use the mul/div command it requires a value to be in EAX register. How can I multiply or divide two constants in Assembly? Here's the code so far... .section .data .global n .equ A, 50 .equ B, 5 .section .text .global loop_function loop_function: # prologue pushl %ebp # save

问题 This question already has answers here : Java: Having trouble declaring an enum with integer constants (3 answers) Closed last year . I'm currently creating integer constants in the following manner. public class Constants { public static int SIGN_CREATE=0; public static int SIGN_CREATE=1; public static int HOME_SCREEN=2; public static int REGISTER_SCREEN=3; } When i try to do this in enum manner public enum PAGE{SIGN_CREATE,SIGN_CREATE,HOME_SCREEN,REGISTER_SCREEN} and When i used PAGE.SIGN

问题 How do you declare compile time constants in Scala? In C# if you declare const int myConst = 5 * 5; myConst is in-lined as the literal 25. Is: final val myConst = 5 * 5 equivalent or is there some other mechanism/ syntax? 回答1: Yes, final val is the proper syntax, with Daniel's caveats. However, in proper Scala style your constants should be camelCase with a capital first letter. Beginning with a capital letter is important if you wish to use your constants in pattern matching. The first

问题 Good day, friends. Once again stupid question about Obj-C from newbie :) I'm trying to implement singleton design pattern in Obj-C: @interface SampleSingleton : NSObject { @private static SampleSingleton* instance; } +(SampleSingleton*) getInstance; Compiler returns error: "expected specifier-qualifier-list before 'static'". 回答1: Please find below the Objective-C code snippet I am using, for proper thread-safe singleton implementation header file : /* * * Singleton interface that match Cocoa

问题 I have looked at quite a few places online and can't seem to find a good explanation as to why we should append an F or L after a value assigned to a C++ constant. For example: const long double MYCONSTANT = 3.0000000L; Can anyone explain why that is necessary? Doesn't the type declaration imply the value assigned to MYCONSTANT is a long double? What is the difference between the above line and const long double MYCONSTANT = 3.0000000; // no 'L' appended Whew! 回答1: Floating-point constants

问题 I want to use a constant in PHP, but I also want to put it inside double quotes like a variable. Is this at all possible? define("TESTER", "World!"); echo "Hello, TESTER"; obviously outputs "Hello, TESTER", but what I really want is something like: $tester = "World!"; echo "Hello, $tester"; outputs "Hello, World!". 回答1: Sorry, that's not the way constants in PHP work. You can put variables in double quotes and heredocs but not constants. 回答2: I recomend you to use concatenation because: When

问题 I'm stepping through the source code of CodeIgniter with Xdebug in NetBeans and I'm looking for a way to see defined constants as they are defined. If it's not possible, are there any other ways to display all defined constants? 回答1: Take a look at the get_defined_constants function. It will return an array of all the defined constants in the code up to the point of the function call. You can then use print_r to print out the array. 回答2: This kind of practice I use is quite decent as it shows

问题 Why do constants in all examples I've seen always start with k? And should I #define constants in header or .m file? I'm new to Objective C, and I don't know C. Is there some tutorial somewhere that explains these sorts of things without assuming knowledge of C? 回答1: Starting constants with a "k" is a legacy of the pre-Mac OS X days. In fact, I think the practice might even come from way back in the day, when the Mac OS was written mostly in Pascal, and the predominant development language

问题 I have a iPhone application with a few custom-defined colors for my theme. Since these colors will be fixed for my UI, I would like to define the colors in a class to be included (Constants.h and Constants.m). How do I do that? (Simply defining them does not work because UIColors are mutable, and would cause errors - Initalizer not constant). /* Constants.h */ extern UIColor *test; /* Constants.m */ UIColor *test = [UIColor colorWithRed:1.0 green:1.0 blue:1.0 alpha:1.0]; Thanks! 回答1: A