type_index is “a simple wrapper for type_info which can be used as an index type in associative containers (23.4) and in unordered associative containers (23.5)”. If you use type_index instead of type_info*, you will free yourself from having to provide an explicit comparator in your maps. The only cost is that you need to #include … Read more
The requirements of the call to the function object Deleter are specific on this as listed in the requirements of the std::unique_ptr<T>::reset() member. From [unique.ptr.single.modifiers]/3, circa N4660 ยง23.11.1.2.5/3; unique_ptr modifiers void reset(pointer p = pointer()) noexcept; Requires: The expression get_deleter()(get()) shall be well formed, shall have well-defined behavior, and shall not throw exceptions. In general … Read more
Is there a reasonably simple way to replace srand() and rand()? Full disclosure: I don’t like rand(). It’s bad, and it’s very easily abused. The C++11 random library fills in a void that has been lacking for a long, long time. The problem with high quality random libraries is that they’re oftentimes hard to use. … Read more
Yes, its a bug. This is something new and was voted in the working paper in February 2012 (link). Nicol Bolas makes a good point in that gcc is actually the conforming compiler according to the FDIS approved C++11 standard because the changes to the working paper were made after that.
Do the arguments in the quotation hold? Measure and you will know. Are you constrained in memory? Can you figure out the correct size up front? It will be more efficient to reserve than it will be to shrink after the fact. In general I am inclined to agree on the premise that most uses … Read more
Yes there is, but you need a different or to put it exactly, the same PRNG on each platform. std::default_random_engine engine is a implementation defined PRNG. That means you may not get the same PRNG on every platform. If you do not have the same one then your chances of getting the same sequence is … Read more
Is it ok to std::move elements out? Yes, it’s okay. If I moved the ith element out, then ith slot goes into an undefined but valid state It leaves the element in a valid but unspecified state. The difference between those two words is important in C++, but probably not too important to this question. … Read more
If I understand it correct, a=std::move(b) binds reference a to the address of b. And after this operation the content that b points to is not guaranteed. Ah, no: a is not necessarily a reference. The above use of std::move also grants the compiler permission to call decltype(a)::operator=(decltype(b)&&) if it exists: such assignment operators are … Read more
First, my advice is to watch CppCon 2015: Stephan T. Lavavej “functional: What’s New, And Proper Usage”. std::binary_function is mentioned on slide 36, at around 36 mins in the video. You can find the slides at github.com/CppCon/CppCon2015). It doesn’t go into detail why you shouldn’t use std::binary_function, but if you’re using something that’s been deprecated … Read more
enable_if works because the substitution of a template argument resulted in an error, and so that substitution is dropped from the overload resolution set and only other viable overloads are considered by the compiler. In your example, there is no substitution occurring when instantiating the member functions because the template argument T is already known … Read more