小编dik*_*231的帖子

我正在尝试将单词从一个文件复制到另一个文件,这是我的代码:

int main()
{

    string from, to;

    cin >> from >> to;

    ifstream ifs(from);

    ofstream ofs(to);

    set<string> words(istream_iterator<string>(ifs), istream_iterator<string>());
    copy(words.begin(), words.end(), ostream_iterator<string>(ofs, "\n"));

    return !ifs.eof() || !ofs;
}

这样我得到一个编译错误:

expression must have class type

在我称之为copy()的行

如果我将迭代器的结构更改为以下它的工作原理:

set<string> words{ istream_iterator<string>{ ifs }, istream_iterator<string>{} };

我想在cpp中初始化对象时选择()和{}只是一个选择问题,但我想我错了.谁可以给我解释一下这个 ？

我知道在网上做这个的例子,但每个例子都不同,我自己的实现也是如此.我试图弄清楚我的实现有什么问题,因为它没有按预期工作.

代码段:

var mousePressX = -1;
var mousePressY = -1;

document.getElementById("contextMenu").addEventListener("mousedown", function(event) {
    mousePressX = event.clientX;
    mousePressY = event.clientY;
}, false);

document.getElementById("contextMenu").addEventListener("mouseup", function(event) {
    mousePressX = -1;
    mousePressY = -1;
}, false);

document.getElementById("contextMenu").addEventListener("mousemove", function(event) {
    if (mousePressX != -1 && mousePressY != -1) {
        repositionElement(event.target, event.clientX, event.clientY);
    }
}, false);

function repositionElement(element, currentMouseX, currentMouseY) {
    element.style.left = element.offsetLeft + (currentMouseX - mousePressX) + 'px';
    element.style.top = element.offsetTop + (currentMouseY - mousePressY) + 'px';
}

jsfiddle:http: //jsfiddle.net/4rLctko8/

无法弄清楚出了什么问题,但我注意到如果我改变以下几行:

element.style.left …