This boils down to whether or not a lambda’s type differs across translation units. If it does, it may affect template argument deduction and potentially cause different functions to be called – in what are meant to be consistent definitions. That would violate the ODR (see below). However, that isn’t intended. In fact, this problem … Read more
You use a move_iterator with insert: v1.insert(v1.end(), make_move_iterator(v2.begin()), make_move_iterator(v2.end())); The example in 24.5.3 is almost exactly this. You’ll get the optimization you want if (a) vector::insert uses iterator-tag dispatch to detect the random-access iterator and precalculate the size (which you’ve assumed it does in your example that copies), and (b) move_iterator preserves the iterator category … Read more
First define the lambda object, then pass it to the template’s type using decltype and also pass it directly to the constructor. auto comp = []( adjist a, adjlist b ) { return a.second > b.second; }; priority_queue< adjlist_edge , vector<adjlist_edge>, decltype( comp ) > adjlist_pq( comp );
For the record, the static constexpr version will work like you’d expected in C++17. From N4618 Annex D.1 [depr.static_constexpr]: D.1 Redeclaration of static constexpr data members [depr.static_constexpr] For compatibility with prior C++ International Standards, a constexpr static data member may be redundantly redeclared outside the class with no initializer. This usage is deprecated. [Example: struct … Read more
If all you want to do is remove trailing zeros, well, that’s easy. std::string str = std::to_string (f); str.erase ( str.find_last_not_of(‘0’) + 1, std::string::npos ); str.erase ( str.find_last_not_of(‘.’) + 1, std::string::npos );
Is this what you’re looking for? #include <chrono> #include <iostream> int main() { typedef std::chrono::high_resolution_clock Time; typedef std::chrono::milliseconds ms; typedef std::chrono::duration<float> fsec; auto t0 = Time::now(); auto t1 = Time::now(); fsec fs = t1 – t0; ms d = std::chrono::duration_cast<ms>(fs); std::cout << fs.count() << “s\n”; std::cout << d.count() << “ms\n”; } which for me prints … Read more
It has a similar syntax, except you remove the identifier from the pointer: using FunctionPtr = void (*)(); Here is an Example If you want to “take away the uglyness”, try what Xeo suggested: #include <type_traits> using FunctionPtr = std::add_pointer<void()>::type; And here is another demo.
It is inlined, but not optimized away because you compiled with -O0 (the default). That generates asm for consistent debugging, allowing you to modify any C++ variable while stopped at a breakpoint on any line. This means the compiler spills everything from registers after every statement, and reloads what it needs for the next. So … Read more
The best practice is not to reuse the pool (what would be the use of pooling, if you keep creating new pools?). If you want to be sure you “time” the batches together, I’d suggest using when_all on futures: Live On Coliru #define BOOST_THREAD_PROVIDES_FUTURE_WHEN_ALL_WHEN_ANY #include <iostream> #include <boost/bind.hpp> #include <boost/asio.hpp> #include <boost/thread.hpp> uint64_t foo(uint64_t begin) … Read more
My take on this. 20.8.10.1.2/10 in N3225 The values of the bound arguments v1, v2, …, vN and their corresponding types V1, V2, …, VN depend on the types TiD derived from the call to bind and the cv-qualifiers cv of the call wrapper g as follows: if TiD is reference_wrapper, the argument is tid.get() … Read more