stl

问题 As constexpr std::string and constexpr std::vector have been accepted into C++20, how will these be used? The linked papers are very short on details. Do we need to specify special constexpr allocators, making compile-time strings/vectors incompatible with their normal equivalents? 回答1: Those two papers depend heavily on P0784, which discusses how allocations at compile-time will work. Incomplete answer: Only std::allocator will work. All allocations are tracked, and must be deallocated

问题 As constexpr std::string and constexpr std::vector have been accepted into C++20, how will these be used? The linked papers are very short on details. Do we need to specify special constexpr allocators, making compile-time strings/vectors incompatible with their normal equivalents? 回答1: Those two papers depend heavily on P0784, which discusses how allocations at compile-time will work. Incomplete answer: Only std::allocator will work. All allocations are tracked, and must be deallocated

问题 I am wanting to do Boolean operations on STL files with geometric primitives from the VTK library. My problem is converting the STL geometry to something that the VTK Boolean objects will except. I tried the following... import vtk filename = 'gyroid.stl' reader = vtk.vtkSTLReader() reader.SetFileName(filename) mapper = vtk.vtkPolyDataMapper() mapper.SetInputConnection(reader.GetOutputPort()) gyroid = vtk.vtkActor() gyroid.SetMapper(mapper) sphere = vtk.vtkSphere() sphere.SetRadius(30) sphere

问题 next_permutation is a C++ function which gives the lexicographically next permutation of a string. Details about its implementation can be obtained from this really awesome post. http://wordaligned.org/articles/next-permutation Is anyone aware of a similar implementation in Python? Is there a direct python equivalent for STL iterators? 回答1: itertools.permutations is close; the biggest difference is it treats all items as unique rather than comparing them. It also doesn't modify the sequence

问题 When std::vector reallocate its memory array, what kind of copy / move constructor is used to copy / move elements to new houses? 回答1: If the move-constructor exists and is noexcept then it is used. Otherwise the copy-constructor is used. Using a move-constructor that might throw is undesirable as it might happen that some objects are moved to the new storage and then an exception prevents the rest of the objects being moved. The cppreference.com site does say that if the object is non

问题 When std::vector reallocate its memory array, what kind of copy / move constructor is used to copy / move elements to new houses? 回答1: If the move-constructor exists and is noexcept then it is used. Otherwise the copy-constructor is used. Using a move-constructor that might throw is undesirable as it might happen that some objects are moved to the new storage and then an exception prevents the rest of the objects being moved. The cppreference.com site does say that if the object is non

问题 When std::vector reallocate its memory array, what kind of copy / move constructor is used to copy / move elements to new houses? 回答1: If the move-constructor exists and is noexcept then it is used. Otherwise the copy-constructor is used. Using a move-constructor that might throw is undesirable as it might happen that some objects are moved to the new storage and then an exception prevents the rest of the objects being moved. The cppreference.com site does say that if the object is non

来源： https://stackoverflow.com/questions/25195233/time-complexity-of-iterating-through-a-c-unordered-map

来源： https://stackoverflow.com/questions/25195233/time-complexity-of-iterating-through-a-c-unordered-map

来源： https://stackoverflow.com/questions/25195233/time-complexity-of-iterating-through-a-c-unordered-map