2014年8月13日 · If there's an efficient X::swap(X&) member then specializing swap(X&, X&) to call it makes sense. Some move operations might even be implemented in terms of the swap member, so the generic std::swap function would call the swap member three times, when it only needs to be done once. –

The copy-and-swap idiom is a way to do just that: It first calls a class' copy constructor to create a temporary object, then swaps its data with the temporary's, and then lets the temporary's destructor destroy the old state. Since swap() is supposed to never fail, the only part which might fail is the copy-construction. That is performed ...

2013年4月23日 · Does C++ have a built in such as part of STL to swap two numerical values instead of doing: int tmp = var1; var1 = var2; var2 = tmp; Something like this: std::swapValues(var1, var2); Where

2011年6月3日 · Using std::swap by including the <algorithm> library to swap values by references / smart pointers, e.g. std::swap(v[0], v[1]) Note: v[i] is a reference. Using std::iter_swap from the same library, e.g. std::iter_swap(v.begin(), v.begin() + v.size() - 1) Using lvalue references and rvalue tuple by including the <tuple> library

2015年11月24日 · The default-construct + swap implementation may appear slower, but -sometimes- data flow analysis in the compiler can eliminate some pointless assignments and end up very similar to handwritten code. This works only for types without "clever" value semantics.

2015年5月11日 · The meeting minutes acknowledge "annoying ADL problems" with std::swap(x, y), but conclude that a swap operator would not address those problems. Because of backwards compatibility, the EWG also believed that if accepted, std::swap and the swap operator would forever co-exist.

2012年7月24日 · Free function in the same namespace allows for ADL to find it, and enables other code to use the common pattern of void swap( other& l, other& r ) { using std::swap; swap( l.t, r.t ); } without having to know whether the type of other::t has an specific swap overload or the one in std:: needs to be used. Forwarding to 3 allows you to provide a ...

2010年7月10日 · The reason an STL friendly class needs swap is that swap is used as a primitive operation in many STL algorithms. (e.g. reverse, sort, partition etc. are typically implemented using swap) Why should a specialized swap be implemented (i.s.o. relying on the default swap)? There are many (good) answers to this part of your question already.

std::swap() is used by many std containers (such as std::list and std::vector) during sorting and even assignment. But the std implementation of swap() is very generalized and rather inefficient for custom types. Thus efficiency can be gained by overloading std::swap() with a custom type specific implementation. But how can you implement it so ...

2014年9月17日 · That's a nice example, thanks. It appears that the standards community have realized the need to swap references and added a workaround to C++11 contrary to the opinion expressed in some other answers here that swapping references is …