declaration

问题 When declaring objects in c++ - What is the difference between MyClass myObj (a,b,c); (I understand this as invoking the constructor that takes three arguments) vs. MyClass myObbj{a,b,c}; Not sure what the curly brackets here mean? As a reference I am using the following code // Inertial Navigation EKF NavEKF EKF{&ahrs, barometer, sonar}; AP_AHRS_NavEKF ahrs{ins, barometer, gps, sonar, EKF}; 1. Is the use of curly brace as in NavEKF EKF{&ahrs, barometer, sonar}; part of c++ standard. gcc 4.6

问题 Before Consider to have a class and a global function: This is, for example, usefulfuncts.hpp void dosome(int a, int b) throw (std::exception); This is usefulfuncts.cpp void dosome(int a, int b) throw (std::exception) { //... } And this is aclass.hpp class aclass { // Members... friend void dosome(int a, int b) throw (std::exception); // Members... }; After (what I would like that to be) Ok! I would like to understand if it is strictly necessary to write everytime the throw clause. So for

问题 int * (*) (int * , int * (*)()) I'd like to know what type is it ? , can someone give an example of a declaration using this type. any help would be great. thanks. 回答1: It is a pointer to function that returns int* and accepts int* and pointer to function that returns int* (and accepts undefined number of parameters; see comments). Some example (does not look very nice, it is just constructed to contain the mentioned declaration): #include <stdio.h> static int a = 10; int* f1() { return &a; }

问题 Is there explicit array initialization (declaration and assignment) in GO or the only way is using the shorthand operator? Here is a practical example - is this two equal: a := [3]int{1, 0, 1} var a [3]int = [3]int{1, 0, 1} 回答1: They are equivalent. In general: Spec: Short variable declaration: A short variable declaration uses the syntax: ShortVarDecl = IdentifierList ":=" ExpressionList . It is shorthand for a regular variable declaration with initializer expressions but no types: "var"

问题 So I need to have a some sort of multiset of characters, where adding a duplicate character increases the cardinality by 1, and the multiplicity of characters should not drastically increase the memory that the object takes up. This will be implemented with some sort of map where characters are keys, that hold a value representing the number of that character is represented in the set. However, I'm struggling to figure out which collection would be best for this (I was looking at hashmap) and

问题 double (*bar(int, double(*)(double,double[])))(double); While reviewing a lecture slide, I found an exercise left to the student: In plain English, what is the type of bar in this C declaration? Please help walk me through this. I don't even know where to begin, except that something is ultimately returning a double. 回答1: This answer is brought to you by the ability to use the Spiral Rule. Being able to understand a complex expression by starting at the unknown element and reading around it

问题 I know, I know, there's a ton of simple answers that cover most cases for how to avoid this. In my case, I want to use user-input info to create CPU players in a game. If the user chooses easy mode, then I want to declare and instantiate an instance of the EasyPlayer class. Otherwise, I want to declare and instantiate an instance of the HardPlayer class. Either way, the specific name of the variable needs to be "cpu" and the rest of the code operates on "cpu" indiscriminately. That is, all

问题 In moderate-sized or even big complex projects separating template declaration and definition is useful to reduce compilation time. However, in a complex code small programmer mistakes may lead to unnoticed behaviour change, e.g. a generic version is called instead of a specialization. Example: Template specialization became invisible due to a missed declaration. ///////////////////// file A.hpp ///////////////////// #include <iostream> template <typename T> class A { public: void foo() { std

问题 I have understood the difference between declaration and definition And I was practicing some question when I hit the doubt, the below code asked me to list out the error in the snippet. f(int a,int b) { int a; a=20; return a; } Why does this gives re-declaration error of a ? Shouldn't it give multiple definition of a because in: f(int a,int b) — here a is defined right? and in the function body, int a is defined again? So why not multiple definition error? 回答1: A definition is always a

问题 a template parameter can be used in another template parameter that follows it this way : template<typename T, T N> struct s { }; But is it possible to reference "T" if it is declared after "N" ? This does not work : template<T N, typename T> struct s { }; Can we help the compiler by pre-declaring "T" or doing anything else ? Thanks by advance. EDIT : as the first two replies were asking "why are you willing to do that ?" I'll explain the goal : I would like to make the compiler infer the