variadic-functions

问题 6.7.2.1 paragraph 14 of my draft of the C99 standard has this to say about unions and pointers (emphasis, as always, added): The size of a union is sufficient to contain the largest of its members. The value of at most one of the members can be stored in a union object at any time. A pointer to a union object, suitably converted, points to each of its members (or if a member is a bit- field, then to the unit in which it resides), and vice versa. All well and good, that means that it is legal

问题 I just found out about a very interesting Java trick: void method1(Integer... a){ } So you can give this method as many integers as you want. Now if I have a similar (overloaded) method like this: void method1(int a, int b){ } Which method runs when I execute the following line: method1(1, 2); Well, I could find that out very easily by just testing it out with different method instructions but when I think about the "rules" in "overloading" methods then I have to make sure that every

问题 private void activateRecords(long[] stuff) { ... api.activateRecords(Arrays.asList(specIdsToActivate)); } Shouldn't this call to Arrays.asList return a list of Long s? Instead it is returning a List<long[]> public static <T> List<T> asList(T... a) The method signature is consistent with the results, the varargs throws the entire array into the list. It's the same as new ArrayList(); list.add(myArray) And yes, I know it's meant to be used like this: Arrays.asList(T t1, T t2, T t3) I guess what

问题 This question already has answers here : Closed 6 years ago . Possible Duplicate: bug with varargs and overloading? could anyone explain me how this one works: class Vararg { static void vararg(int... x) { System.out.println("Integer..."); } static void vararg(long... x) { System.out.println("long..."); } public static void main(String [] args) { int s = 0; vararg(s,s); } } Get compile time error class Vararg { static void vararg(Integer... x) { System.out.println("Integer..."); } static void

问题 I am using IntelliJ IDEA with javac on JDK 1.8. I have the following code: class Test<T extends Throwable> { @SafeVarargs final void varargsMethod( Collection<T>... varargs ) { arrayMethod( varargs ); } void arrayMethod( Collection<T>[] args ) { } } IntelliJ IDEA does not highlight anything in the above code as a warning. However, when compiling, the following line appears in the "Make" tab of the "Messages" view: Warning:(L, C) java: Varargs method could cause heap pollution from non

问题 I have some varargs system function, where T is some actual type, like String : sys(T... args) I want to create own function, which delegates to the system function. My function is also a varargs function. I want to pass through all the arguments for my function through to the system function, plus an additional trailing argument. Something like this: myfunc(T... args) { T myobj = new T(); sys(args, myobj); // <- of course, here error. } How do I need to change the line with the error? Now I

问题 Could someone help me understand section 15.12.2.5 of the JLS re: most specific method? (bludgeoned cut&paste from JLS follows) In addition, one variable arity member method named m is more specific than another variable arity member method of the same name if either: One member method has n parameters and the other has k parameters, where n >= k. The types of the parameters of the first member method are T1, . . . , Tn-1 , Tn[], the types of the parameters of the other method are U1, . . . ,

问题 my problem with vsprintf is that I can not obtain input arguments directly, I have to first get inputs one by one and save them in void** , then pass this void** to vsprintf() , it is all fine for windows, but when I come to 64bit linux, gcc cannot compile because it is not allowed to convert from void** to va_list , Is there anyone that can give me some help how I should do this under linux? Can I create va_list dynamically in GCC? void getInputArgs(char* str, char* format, ...) { va_list

问题 Suppose I have a variadic template function like template<typename... Args> unsigned length(Args... args); How do I find the length of the parameter list using the length function ? 回答1: Use sizeof... : template<typename... Args> constexpr std::size_t length(Args...) { return sizeof...(Args); } Note you shouldn't be using unsigned , but std::size_t (defined in <cstddef> ). Also, the function should be a constant expression. Without using sizeof... : namespace detail { template<typename T>

问题 In Python and others, there's special syntax for variable length argument lists: def do_something(*args): # do something do_something(1, 2, 3, 4, 5, ...) # arbitrarily long list I was reading the PHP manual, and it said this: PHP 4 and above has support for variable-length argument lists in user-defined functions. This is really quite easy, using the func_num_args(), func_get_arg(), and func_get_args() functions. No special syntax is required, and argument lists may still be explicitly