Tutorial by Examples: v

Expressions in C++ are assigned a particular value category, based on the result of those expressions. Value categories for expressions can affect C++ function overload resolution. Value categories determines two important-but-separate properties about an expression. One property is whether the exp...

A prvalue (pure-rvalue) expression is an expression which lacks identity, whose evaluation is typically used to initialize an object, and which can be implicitly moved from. These include, but are not limited to: Expressions that represent temporary objects, such as std::string("123"). ...

An xvalue (eXpiring value) expression is an expression which has identity and represents an object which can be implicitly moved from. The general idea with xvalue expressions is that the object they represent is going to be destroyed soon (hence the "eXpiring" part), and therefore implici...

An lvalue expression is an expression which has identity, but cannot be implicitly moved from. Among these are expressions that consist of a variable name, function name, expressions that are built-in dereference operator uses and expressions that refer to lvalue references. The typical lvalue is s...

A glvalue (a "generalized lvalue") expression is any expression which has identity, regardless of whether it can be moved from or not. This category includes lvalues (expressions that have identity but can't be moved from) and xvalues (expressions that have identity, and can be moved from)...

An rvalue expression is any expression which can be implicitly moved from, regardless of whether it has identity. More precisely, rvalue expressions may be used as the argument to a function that takes a parameter of type T && (where T is the type of expr). Only rvalue expressions may be gi...

Anonymous types allow the creation of objects without having to explicitly define their types ahead of time, while maintaining static type checking. var anon = new { Value = 1 }; Console.WriteLine(anon.Id); // compile time error Conversely, dynamic has dynamic type checking, opting for runtime ...

To remove a cookie, set the expiry timestamp to a time in the past. This triggers the browser's removal mechanism: setcookie('user', '', time() - 3600, '/'); When deleting a cookie make sure the path and domain parameters of setcookie() matches the cookie you're trying to delete or a new cooki...

A view can filter some rows from the base table or project only some columns from it: CREATE VIEW new_employees_details AS SELECT E.id, Fname, Salary, Hire_date FROM Employees E WHERE hire_date > date '2015-01-01'; If you select form the view: select * from new_employees_details IdFNam...

A view can be a really complex query(aggregations, joins, subqueries, etc). Just be sure you add column names for everything you select: Create VIEW dept_income AS SELECT d.Name as DepartmentName, sum(e.salary) as TotalSalary FROM Employees e JOIN Departments d on e.DepartmentId = d.id GROUP BY...

What is Serialization Serialization is the process of converting an object's state (including its references) to a sequence of bytes, as well as the process of rebuilding those bytes into a live object at some future time. Serialization is used when you want to persist the object. It is also used b...

It is possible to instruct the Xamarin.Android Bindings Generator to ignore a Java type and not bind it. This is done by adding a remove-node XML element to the metadata.xml file: <remove-node path="/api/package[@name='{package_name}']/class[@name='{name}']" />

Mark your UIView subclass as an accessible element so that it is visible to VoiceOver. myView.isAccessibilityElement = YES; Ensure that the view speaks a meaningful label, value, and hint. Apple provides more details on how to choose good descriptions in the Accessibility Programming Guide.

Modal views completely capture the user’s attention until a task is complete. iOS clarifies this to users by dimming and disabling all other content when a modal view, such as an alert or popover, is visible. An app that implements a custom modal interface needs to hint to VoiceOver that this view d...

1.8 You can remove a submodule (e.g. the_submodule) by calling: $ git submodule deinit the_submodule $ git rm the_submodule git submodule deinit the_submodule deletes the_submodules' entry from .git/config. This excludes the_submodule from git submodule update, git submodule sync and git ...

You can use a template in a function based view as follows: from django.shortcuts import render def view(request): return render(request, "template.html") If you want to use template variables, you can do so as follows: from django.shortcuts import render def view(request):...

Chef Scollector Cookbook: https://github.com/alexmbird/chef-scollector Chef Bosun Cookbook: https://github.com/ptqa/chef-bosun Puppet scollector module: https://github.com/axibase/axibase-puppet-modules Bosun Ansible/Vagrant example: https://github.com/gnosek/bosun-deploy

To explicitly declare variables in VBA, use the Dim statement, followed by the variable name and type. If a variable is used without being declared, or if no type is specified, it will be assigned the type Variant. Use the Option Explicit statement on first line of a module to force all variables t...

public class CustomFormat : IFormatProvider, ICustomFormatter { public string Format(string format, object arg, IFormatProvider formatProvider) { if (!this.Equals(formatProvider)) { return null; } if (format == "Reverse") ...

SQL injection is a kind of attack that allows a malicious user to modify the SQL query, adding unwanted commands to it. For example, the following code is vulnerable: // Do not use this vulnerable code! $sql = 'SELECT name, email, user_level FROM users WHERE userID = ' . $_GET['user']; $conn->...