construction

问题 I recently started using Haskell and it will probably be for a short while. Just being asked to use it to better understand functional programming for a class I am taking at Uni. Now I have a slight problem I am currently facing with what I am trying to do. I want to build it breadth-first but I think I got my conditions messed up or my conditions are also just wrong. So essentially if I give it [“A1-Gate”, “North-Region”, “South-Region”, “Convention Center”, “Rectorate”, “Academic Building1”

问题 I recently started using Haskell and it will probably be for a short while. Just being asked to use it to better understand functional programming for a class I am taking at Uni. Now I have a slight problem I am currently facing with what I am trying to do. I want to build it breadth-first but I think I got my conditions messed up or my conditions are also just wrong. So essentially if I give it [“A1-Gate”, “North-Region”, “South-Region”, “Convention Center”, “Rectorate”, “Academic Building1”

问题 Is there a way to implement a singleton object in C++ that is: Lazily constructed in a thread safe manner (two threads might simultaneously be the first user of the singleton - it should still only be constructed once). Doesn't rely on static variables being constructed beforehand (so the singleton object is itself safe to use during the construction of static variables). (I don't know my C++ well enough, but is it the case that integral and constant static variables are initialized before

问题 Is there a way to implement a singleton object in C++ that is: Lazily constructed in a thread safe manner (two threads might simultaneously be the first user of the singleton - it should still only be constructed once). Doesn't rely on static variables being constructed beforehand (so the singleton object is itself safe to use during the construction of static variables). (I don't know my C++ well enough, but is it the case that integral and constant static variables are initialized before

问题 Is there a way to implement a singleton object in C++ that is: Lazily constructed in a thread safe manner (two threads might simultaneously be the first user of the singleton - it should still only be constructed once). Doesn't rely on static variables being constructed beforehand (so the singleton object is itself safe to use during the construction of static variables). (I don't know my C++ well enough, but is it the case that integral and constant static variables are initialized before

问题 Is there a way to implement a singleton object in C++ that is: Lazily constructed in a thread safe manner (two threads might simultaneously be the first user of the singleton - it should still only be constructed once). Doesn't rely on static variables being constructed beforehand (so the singleton object is itself safe to use during the construction of static variables). (I don't know my C++ well enough, but is it the case that integral and constant static variables are initialized before

问题 Is there a way to implement a singleton object in C++ that is: Lazily constructed in a thread safe manner (two threads might simultaneously be the first user of the singleton - it should still only be constructed once). Doesn't rely on static variables being constructed beforehand (so the singleton object is itself safe to use during the construction of static variables). (I don't know my C++ well enough, but is it the case that integral and constant static variables are initialized before

问题 I'm facing some strange behavior with thread_local and not sure whether I'm doing something wrong or it's a GCC bug. I have the following minimal repro scenario: #include <iostream> using namespace std; struct bar { struct foo { foo () { cerr << "foo" << endl; } int i = 42; }; static thread_local foo FOO; }; static thread_local bar::foo FREE_FOO; thread_local bar::foo bar::FOO; int main() { bar b; cerr << "main" << endl; // cerr << FREE_FOO.i << endl; cerr << b.FOO.i << endl; return 0; } With

问题 Lately I ran into a problem which somehow (but only somehow) makes sense to me. It is based on interpreting the construction of a temporary as declaration of the single (!) constructor argument. Please have a look at the minimal example below. #include <iostream> class Foo0{ public: Foo0(int a){}; void doStuff() {std::cout<<"maap"<<std::endl;}; }; class Foo1{ public: Foo1(int a){}; void doStuff() {std::cout<<"maap"<<std::endl;}; }; class Foo2{ public: Foo2(int a){}; void doStuff() {std::cout<

问题 This has been running through my mind as a possible solution to an issue, however as it is a fairly obvious technical violation of something in C++, I wanted to know how likely to it is to fail, whether there is another fairly obvious approach, etc. I'm hoping this doesn't get into a flamewar about undefined behavior, but considering the topic I do expect a little bit. This is not the code I'm writing, I'm hoping it's not too simplified to not describe what I am attempting to do. class Code {