lambda

问题 Reading up on lambdas, I tried understanding them capturing this and *this . I wrote a small test: #include <iostream> #include <functional> using namespace std; struct A { int x = 0; function<int(void)> get_x_cpy = [=, this]() { return x++; }; function<int(void)> get_x_ref = [&, this]() { return x++; }; }; int main() { A a; cout << a.get_x_cpy() << a.get_x_cpy() << a.get_x_ref() << a.get_x_ref() << '\n'; } and, expecting the get_x_cpy() to make a copy of a I expected to see 0001 or 0101

问题 Reading up on lambdas, I tried understanding them capturing this and *this . I wrote a small test: #include <iostream> #include <functional> using namespace std; struct A { int x = 0; function<int(void)> get_x_cpy = [=, this]() { return x++; }; function<int(void)> get_x_ref = [&, this]() { return x++; }; }; int main() { A a; cout << a.get_x_cpy() << a.get_x_cpy() << a.get_x_ref() << a.get_x_ref() << '\n'; } and, expecting the get_x_cpy() to make a copy of a I expected to see 0001 or 0101

问题 Reading up on lambdas, I tried understanding them capturing this and *this . I wrote a small test: #include <iostream> #include <functional> using namespace std; struct A { int x = 0; function<int(void)> get_x_cpy = [=, this]() { return x++; }; function<int(void)> get_x_ref = [&, this]() { return x++; }; }; int main() { A a; cout << a.get_x_cpy() << a.get_x_cpy() << a.get_x_ref() << a.get_x_ref() << '\n'; } and, expecting the get_x_cpy() to make a copy of a I expected to see 0001 or 0101

问题 Note: please pay attention carefully this is not a duplicate. I need to create the following Lambda expression: () => model.property the model and its property will be determine at runtime. I want a function that takes the model and property and generate the expression: public object GenerateLambda(object model, string property) { } If it is possible I don't want the function to be generic. but I think the main problem that I have is with () expression. Update : The return type of

问题 Note: please pay attention carefully this is not a duplicate. I need to create the following Lambda expression: () => model.property the model and its property will be determine at runtime. I want a function that takes the model and property and generate the expression: public object GenerateLambda(object model, string property) { } If it is possible I don't want the function to be generic. but I think the main problem that I have is with () expression. Update : The return type of

问题 I have an API for managing a camera configuration. There are 344 individual options to manage. When a certain value changes the API calls a callback function to notify the program. The register function takes a void RegisterCallback(Option * ptr, void (fn*)(void*)) function pointer as a callback function. I cannot use a single function for callback, because I do now where is the callback coming from . One solution is to create 344 individual callback functions: void callback0(void*); void

问题 This question already has an answer here : Java8 Effectively Final compile time error on non final variable (1 answer) Closed 3 years ago . I am trying to return a boolean for the result. public boolean status(List<String> myArray) { boolean statusOk = false; myArray.stream().forEach(item -> { helpFunction(item).map ( x -> { statusOk = x.status(); // x.status() returns a boolean if (x.status()) { return true; } return false; }); }); } It's complaining variable used in lambda expression should

问题 I have the following list of Employee data which I need to group based on the employee department and then I want to find the 2 highest-paid employees in each department. public class Employee { private int id; private String name; private String dept; private int salary; //setters and getters } List<Employee> listOfEmp = new ArrayList<>(); listOfEmp.add(new Employee (1, "A", "IT",100)); listOfEmp.add(new Employee (2, "B", "IT",200)); listOfEmp.add(new Employee (3, "C", "SUPPORT",100));

问题 I have the following list of Employee data which I need to group based on the employee department and then I want to find the 2 highest-paid employees in each department. public class Employee { private int id; private String name; private String dept; private int salary; //setters and getters } List<Employee> listOfEmp = new ArrayList<>(); listOfEmp.add(new Employee (1, "A", "IT",100)); listOfEmp.add(new Employee (2, "B", "IT",200)); listOfEmp.add(new Employee (3, "C", "SUPPORT",100));

问题 I want to know what exactly is lambda in python? and where and why it is used. thanks 回答1: Lambda is more of a concept or programming technique then anything else. Basically it's the idea that you get a function (a first-class object in python) returned as a result of another function instead of an object or primitive type. I know, it's confusing. See this example from the python documentation: def make_incrementor(n): return lambda x: x + n f = make_incrementor(42) f(0) >>> 42 f(1) >>> 43 So