metaprogramming

问题 I have a a set of overloads of a commutative binary function named overlap , which accepts two distinct types: class A a; class B b; bool overlap(A, B); bool overlap(B, A); My function overlap returns true if and only if one shape overlaps the other - this is one common example used when discussing multimethods. Because overlap(a, b) is equivalent to overlap(b, a) , I only need to implement one "side" of the relation. One repetitive solution is to write something like this: bool overlap(A a,

问题 Test controller is as follows def justTest(){ def res = paymentService.justTest() [status: res.status] } Test service method is as follows def justTest(){ } Now the two test cases are as follows. Payment service method justTest was modified in both cases to return two different values. @Test void test1(){ PaymentService.metaClass.justTest = {['status': true]} def res = controller.justTest() assertEquals(res.status, true) GroovySystem.metaClassRegistry.removeMetaClass(PaymentService.class) }

问题 How do I find out if a variable has been defined in my Robot Framework script? I am doing API testing, not UI testing. I have a complex set up and tear-down sequence and, since I am interacting with multiple computers through the script, it is important to know the current state if a fatal error has occurred. I could track what I have done with some complex set of meta variables or a variable tracking list, but I would prefer to query if a particular variable has been defined and if so take

问题 How do I find out if a variable has been defined in my Robot Framework script? I am doing API testing, not UI testing. I have a complex set up and tear-down sequence and, since I am interacting with multiple computers through the script, it is important to know the current state if a fatal error has occurred. I could track what I have done with some complex set of meta variables or a variable tracking list, but I would prefer to query if a particular variable has been defined and if so take

问题 I'm trying to understand how enable_if works and I understand almost everything except scenario #3 from https://en.cppreference.com/w/cpp/types/enable_if template<class T> void destroy(T* t, typename std::enable_if<std::is_trivially_destructible<T>::value>::type* = 0) { std::cout << "destroying trivially destructible T\n"; } if the expression in enable_if is true then partial template specialization is chosen, so if it is chosen: why in enable_if is only condition without indicating second

问题 The title is rather hard to formulate in word, but here is what I'm trying to achieve in non-compileable code: template<template <typename> class Container> Container<int> foo() { return Container<int>{1,2,3}; } int main() { auto bar = foo<std::vector>(); return 0; } Basically I want a template function that can "compose" its return type from a type that is passed to it and a previously known type (in this case int ). In this case I want a function that returns an arbitrary data type inside a

问题 for primary template: template<typename A, typename B> class MyClass {... with template specialization, what is the difference between template<typename A, typename B> class MyClass<int, float> {... and template<> class MyClass<int, float> {... 回答1: template<typename A, typename B> class MyClass<int, float> {... should be not allowed. Indeed, if you specify the formal parameters A and B , your template should be using them. The second case is just normal: you say that you are making

问题 for primary template: template<typename A, typename B> class MyClass {... with template specialization, what is the difference between template<typename A, typename B> class MyClass<int, float> {... and template<> class MyClass<int, float> {... 回答1: template<typename A, typename B> class MyClass<int, float> {... should be not allowed. Indeed, if you specify the formal parameters A and B , your template should be using them. The second case is just normal: you say that you are making

问题 I've written a for_each for tuple s: template <typename Tuple, typename F, size_t begin, size_t end> enable_if_t<begin == end || tuple_size<Tuple>::value < end> for_each(Tuple&, F&&) { } template <typename Tuple, typename F, size_t begin = 0U, size_t end = tuple_size<Tuple>::value> enable_if_t<begin < end && tuple_size<Tuple>::value >= end> for_each(Tuple& t, F&& f) { f(get<begin>(t)); for_each<Tuple, F, begin + 1, end>(t, forward<F>(f)); } [Live Example] But Yakk's answer to this question

问题 This question already has answers here : How to find out who called a method? (9 answers) Closed 5 years ago . So I have a rather complex application that I've, perhaps naively, agreed to "debug". Upon entering into a certain method, I'd like to print out as much info about who called the method, from which class, method, etc. it was called from. Any suggestions would be very much appreciated!! 回答1: Just add in your method: NSLog(@"Show stack trace: %@", [NSThread callStackSymbols]); 回答2: For