move

问题 In my simple code, a red ball is falling down in a straight line (that's working). When I push the right arrow key, I want the ball to also move in right direction. This is not working, however. What am I doing wrong? from tkinter import * root = Tk() canvas = Canvas(root, height=400, width=500, background='black') canvas.pack() class Bird: def __init__(self, canvas, coords): self.canvas = canvas self.coords = coords self.bird = canvas.create_rectangle(coords, fill='red') def gravity(self):

问题 I have multiple folders in my ubuntu 16.04 with pictures in them. I would like to move all pictures to one folder and rename all files with same name. I can easily move pictures from first folder, but how do i copy pictures from rest of the folders without destroying (copying over) all existing files with same name? Is there some handy oneliner that i could use in terminal for this? 回答1: cp has a useful option --backup=numbered that adds a numbered suffix to the name of a file that would

问题 I have this simple class: struct Worker { Worker() : done{false} {} Worker(const Worker& rhs) : done{rhs.done}, qworker{} {} Worker(Worker &&rhs) : done{rhs.done} { qworker = std::move(rhs.qworker); } ... } this compile fine with gcc-4.7.2 but if I try to use this version I obtain an error struct Worker { Worker() : done{false} {} Worker(const Worker& rhs) : done{rhs.done}, qworker{} {} Worker(Worker &&rhs) : done{rhs.done} , qworker{std::move(rhs.qworker)} // <- ERROR { } ... } Why? In file

问题 This is a bit theoretical question, but although I have some basic understanding of the std::move Im still not certain if it provides some additional functionality to the language that theoretically couldnt be achieved with supersmart compilers. I know that code like : { std::string s1="STL"; std::string s2(std::move(s1)); std::cout << s1 <<std::endl; } is a new semantic behavior not just performance sugar. :D But tbh I guess nobody will use var x after doing std::move(x). Also for movable

问题 Given the following: Foo getFoo() { Foo result = doSomeWork(); return result; } Does C++ guarantee that result will be moved, instead of copied? Or to put it another way, is writing return std::move(result) superfluous? Are there any (other) situations where the standard specifies that a lvalue will be silently moved instead of copied, in the absence of an explicit std::move cast? Notes: Assume Foo is move-constructible. Disregarding copy/move elision, which may apply in addition. 回答1:

问题 Given the following: Foo getFoo() { Foo result = doSomeWork(); return result; } Does C++ guarantee that result will be moved, instead of copied? Or to put it another way, is writing return std::move(result) superfluous? Are there any (other) situations where the standard specifies that a lvalue will be silently moved instead of copied, in the absence of an explicit std::move cast? Notes: Assume Foo is move-constructible. Disregarding copy/move elision, which may apply in addition. 回答1:

问题 Given the following: Foo getFoo() { Foo result = doSomeWork(); return result; } Does C++ guarantee that result will be moved, instead of copied? Or to put it another way, is writing return std::move(result) superfluous? Are there any (other) situations where the standard specifies that a lvalue will be silently moved instead of copied, in the absence of an explicit std::move cast? Notes: Assume Foo is move-constructible. Disregarding copy/move elision, which may apply in addition. 回答1:

问题 I have a problem in RecyclerView . When I move item in RV and then scroll, saw some items has duplicated. 回答1: RecyclerView will recycle the view.When you delete data,call notifyItemChanged(pos) or notifyDataSetChanged() method. 回答2: I know its late but hope it will help someone. Override these two methods in your adapter. @Override public long getItemId(int position) { return position; } @Override public int getItemViewType(int position) { return position; } 回答3: It is your

问题 I was reading the documentation for std::for_each here http://en.cppreference.com/w/cpp/algorithm/for_each and saw that the return value is std::move(f) Why does the standard enforce moving the input parameter in the return value? Won't it be moved by default anyway, since the input parameter is passed by value? This leads me to a couple of followups, when you compile the following code Something function(Something something) { return something; } The return statement is a move on my system

问题 class Foo { std::vector<SomeType> data_; }; Say Foo can only be constructed by make a copy (technically I mean a copy or move) of a std::vector<SomeType> object. What's the best way to write constructor(s) for Foo ? My first feeling is Foo(std::vector<SomeType> data) noexcept : data_(std::move(data)) {}; Using it, construction of an instance takes 0 or 1 times of vector copy, depending on whether the argument for {data} is moveable or not. 回答1: Your first feeling is good. Strictly speaking it