auto | 易学教程

jQuery实现鼠标悬停显示提示信息窗口的方法

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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" " http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd " > <html xmlns= " http://www.w3.org/1999/xhtml " > <head> <title>鼠标悬停显示提示信息窗口</title> <meta http-equiv= "content-type" content= "text/html;charset=gb2312" > <style type= "text/css" > .contact{width:100px;height:15px; margin:20px 0 0 50px; padding: 0px 0px 0px 5px; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; border-left: 3px

CSS布局基础

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CSS布局基础 1.块区域介绍 1: <body> 2: <div> 3: <p>This is a pargraph.</p> 4: </div> 5: </body> p 元素的包含块是 div 元素，因为作为块级元素，表单元格或行内元素，这是最近的祖先元素，类似的，div的包含块是 body. 因此，p的布局依赖于 div的布局，而div的布局则依赖于 body的布局。块级元素会自动重启一行。 2. 块级元素正常流布局一般的，一个元素的width被定义为从左内边界到右内边界，height则是从上内边界到下内边界的距离。不同的宽度，高度，内边距和外边距相结合，就可以确定文档的布局。水平布局简单规则，正常流中块级元素框的水平部分总和就等于父元素的 width . 假设一个div中有两个段落，这两个段落的外边距设置为 1 em，段落内容宽度 width 在加上其左，右内边距，边框或外边距加在一起正好是div内容的width. 7大属性，margin-left, border-left, padding-left, width, padding-right, border-right, margin-right 这 7 个属性的值加在一起必须是父块元素的width值. ( 其中 margin-left, margin-right, width 可以设置成auto )

第二章基本语言

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第一节语言特性、工程构成、可移植性语言特性：过程式、对象式的程序设计 a. 面向过程的程序设计（过程式的程序设计：c语言程序设计）：从上往下，逐步求精，按顺序一步一步把问题解决结构：学生：学号，名字，性别，成绩在c语言中，要用结构的话，需要定义一个数与该结构的变量 b. 基于对象的程序设计和面向对象的程序设计在C++中，把结构叫成‘类’，如果要使用类，这里就不叫定义结构变量，而是叫做定义一个对象；在类中除了可以定义成员变量还可以定义一些成员函数。这种功能包含在类中，需要的时候通过定义一个对象的方式来调用程序。这种程序书写的方式，就叫做基于对象的程序设计方法。 C++语言有下面特性：继承性（类的继承）多态性（父类和子类同名函数的调用）以上特性升华了基于对象的程序设计，叫面向对象的程序设计面向对象程序设计的优点：易维护易扩展模块化：通过设计各种访问级别，来限制别人对类的访问，也保护了数据的安全。可移植性不同系统可以移植源代码，但是不能移植二进制文件。第二节命名空间简介、基本输入输出精解命名空间概念简介如果在同一个project里面有两个cpp文件写了一个同名函数，那么在编译的时候后面的文件会报错，因为命名冲突了。命名空间就是为了防止名字冲突而引入的一种机制。系统中可以定义多个命名空间，每个命名空间都有自己的名字，不可以同名

What is the auto Bracketed List Syntax?

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问题 W.F. gave a now-deleted answer to my question here which used the line: auto [x, y] = div_t{ 1, 0 }; From the code in the answer it looks like that's like a tie for the div_t struct. I was hoping that someone could explain what was going on here. The complete function code was as follows: constexpr bool first_quot() { auto [x, y] = std::div_t{1, 0}; (void)y; return x; } 回答1: In the most most recent draft of the C++17 specification it's called "Decomposition declarations" and is defined in

How to use auto return and decltype when class members involved with c++11? [duplicate]

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问题 This question already has answers here : decltype as a return type in class member function (3 answers) Closed 2 years ago . For example struct A { auto count() -> decltype(m_count) { return m_count; } int m_count; }; The above gets compilation error because m_count in decltype is not recognized. How to work around it? auto return and get the type from m_count must be used. The code compiles when the order is changed struct A { int m_count; auto count() -> decltype(m_count) { return m_count;

C++ error: no matching function for call to 'print_size'

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问题 I have this code: #include <iostream> #include <vector> template<typename T> void print_size(std::vector<T> a) { std::cout << a.size() << '\n'; } int main() { std::vector<int> v {1, 2, 3}; print_size(v); auto w = {1, 2, 3}; // print_size(w); // error: no matching function for call to 'print_size' // candidate template ignored: could not match 'vector' against 'initializer_list' } ...which compiles and runs without any issues. But if I enable the commented-out line, it produces the error no

bootstrap-select 插件使用详解

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一、简单使用示例 1、下载bootstrap-select，创建页面SelectDemo，页面中添加如下引用 <script src="Scripts/bootstrap-select/js/bootstrap-select.min.js"></script> <script src="Scripts/bootstrap-select/js/i18n/defaults-zh_CN.min.js"></script> <link href="Scripts/bootstrap-select/css/bootstrap-select.min.css" rel="stylesheet" /> HTML代码： <div class="form-group"> 基础下拉： <select id="basicSelect"> <option value="1">常学</option> <option value="2">清华</option> <option value="3">北大</option> <option value="4">河学</option> </select> </div> <div class="form-group"> 下拉多选： <select id="multiSelect" multiple> <option value="1">常学</option>

Is it safe to use `for(auto& e : cont)`? What is wrong with vector<bool>?

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问题 I have found that for (auto& e : cont) is sometimes used instead of ordinary for (auto e : cont) (where cont is some container, e.g. std::vector ). I have found two reasons for it so far: Taking a reference should avoid copying the object (faster execution) Making a copy may be forbidden for some classes (e.g. std::thread ) After few tests I can see: for (auto& e : cont) works with any std::vector<T> except std::vector<bool> for (cont::reference e : cont) works with any std::vector<T>

C++11 auto and size_type

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问题 Given the following usage of auto : std::vector<int> v; for (auto i = 0; i < v.size(); ++i) { ... } It would be ideal for C++ to deduce i as std::vector<int>::size_type , but if it only looks at the initializer for i , it would see an integer. What is the deduced type of i in this case? Is this appropriate usage of auto ? 回答1: Use decltype instead of auto to declare i . for( decltype(v.size()) i = 0; i < v.size(); ++i ) { // ... } Even better, use iterators to iterate over the vector as

C++14 auto deduction error: function returns an array

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问题 community! I'm trying to apply new C++14 features and unexpectedly encountered on error while I was attempting to pass the const char[] argument to the function given below: decltype(auto) autofunc( const auto& a) { cout<<"Hello World\n"; cout<<a<<endl; } auto lambd = [](const auto& word){ autofunc(std::forward< decltype(word) > (word));}; int main() { lambd("Goodbye World\n"); return 0; } I don't know why,but the compilier's message is that function tries to return an array (why would it do