syntax

问题 Simple question: How do I get this to work? struct A { double whatever; std::unordered_map<std::string, A> mapToMoreA; } g++ error: std::pair<_T1, _T2>::second has incomplete type As far as I understand, when instantiating the map, the compiler needs to know the size of A, but it doesn't know this because the map is declared in A's declaration, so is the only way to get around this to use pointers to A (don't feel like doing that)? 回答1: Most of the time it will depend on the container

问题 I know I can do this: void someMethod(){ return; } but I get a syntax error on void someMethod(){ return void; } Why is the latter not allowed? It makes more sense to me. Edit: I know what a void method is, and that I don't have to return from it at all(and probably shouldn't, in most cases) but I don't understand why I can't return void from a void method. In my opinion, there should be no keyword in the method declaration (like constructors) if the you are able to write return;. 回答1: I

问题 Exploring the difference between help and get-help I did: cd Function: get-content help all the input-parameter are defined like: [string]${Name} $ =initiate a variable, {} a hashtable?? Thanks for your help. 回答1: For the official documentation, see the conceptual about_Variables help topic (invoke it with help about_Variables ), and in particular its "Variable Names that Include Special Characters" section. Enclosing the name of a variable in {...} - e.g. ${foo} - unambiguously delimits the

问题 Sometimes I see syntax like this. template<typename T,typename = int> int foo(){ //... } what part typename = int mean? Where it can be used? 回答1: foo has two template arguments. The first is called T and the second is unnamed and defaults to int . In your piece of code alone there is no reason to use the second argument. Unnamed template arguments often come up with SFINAE. An example from cppreference: // primary template handles non-referenceable types: template<class T, class = void>

问题 This question already has answers here : What is %pylab? (5 answers) Closed 6 years ago . I was working on a project in which I had to write %matplotlib inline at the beginning to solve a problem. But I'm wondering what does this "%" stands for: is it an operator ? Has it a name so I could do some researches about it ? 回答1: You are not looking at standard Python code. You are almost certainly using an IPython interactive session, and it uses % as a prefix to recognize special commands, called

问题 This question already has answers here : What is %pylab? (5 answers) Closed 6 years ago . I was working on a project in which I had to write %matplotlib inline at the beginning to solve a problem. But I'm wondering what does this "%" stands for: is it an operator ? Has it a name so I could do some researches about it ? 回答1: You are not looking at standard Python code. You are almost certainly using an IPython interactive session, and it uses % as a prefix to recognize special commands, called

问题 template<typename A, typename B> class mindF_ck { template<typename C> inline bool ouch(C & c_in); }; How do I define the signature for ouch out-of-class ? I send a query to my brain but it keeps coming up blank ;) 回答1: template<typename A, typename B> template<typename C> bool mindf_uck<A,B>::ouch(C & c_in) { } 回答2: template <typename A, typename B> template <typename C> bool mindf_ck<A, B>::ouch(C& c_in) { // ... code ... } 来源： https://stackoverflow.com/questions/5895179/syntax-of-out-of

问题 I have SQL Server 2012 Management Studio. I am trying to create tables using commands. After creating the table, I try to use the DESC command to view the table structure but it shows error saying incorrect syntax near the keyword 'DESC'. The statement is: DESC doughnut_list; 回答1: You may try to use it like this:- exec sp_columns doughnut_list DESC is not an SQL command, it is used in Oracle. You may also try to check sp_columns Also if you want to view the table defintion you may try use

问题 Im using Intellij Idea for some ES Harmony app. With modules syntax I want my IDE to do not highlight this as errors: import $ from "jquery"; I have turned ES Harmony support in project settings, but it does not help. Thanks! 回答1: In case somebody here is still experiencing Issues with ECMAScript 6, you have to enable it in IntelliJ. and after activating ecmascript, set it as JavaScript Language Version: 回答2: Try an EAP version, it technically has support but it is not currently working for

问题 I was trying to compile a program with cmake , and I ended up deleting my main.cpp file, which I had just compounded into another file which held the name of my project (i.e., I just cut and pasted the main function into that one). The problem is that I got a main.cpp not found error, and wasn't sure whether or not in C++ a file known as main.cpp is required, or can I have a file with a different title which contains the function main instead? Edit I should note that I have removed any