Tutorial by Examples: er

Use Case CASE can be used in conjunction with SUM to return a count of only those items matching a pre-defined condition. (This is similar to COUNTIF in Excel.) The trick is to return binary results indicating matches, so the "1"s returned for matching entries can be summed for a count o...

Given that the module from the Defining a Module section exists in the file test.js, you can import from that module and use its exported members: import {doSomething, MyClass, PI} from './test' doSomething() const mine = new MyClass() mine.test() console.log(PI) The somethingPrivate()...

Sometimes you may encounter members that have really long member names, such as thisIsWayTooLongOfAName(). In this case, you can import the member and give it a shorter name to use in your current module: import {thisIsWayTooLongOfAName as shortName} from 'module' shortName() You can import m...

Common values from both sets: You can use the intersect(_:) method to create a new set containing all the values common to both sets. let favoriteColors: Set = ["Red", "Blue", "Green"] let newColors: Set = ["Purple", "Orange", "Green"] ...

Counter is a dict sub class that allows you to easily count objects. It has utility methods for working with the frequencies of the objects that you are counting. import collections counts = collections.Counter([1,2,3]) the above code creates an object, counts, which has the frequencies of all ...

These are all equivalent, the code inside the blocks will run when the document is ready: $(function() { // code }); $().ready(function() { // code }); $(document).ready(function() { // code }); Because these are equivalent the first is the recommended form, the following is a ...

# Length of a string $ var='12345' $ echo "${#var}" 5 Note that it's the length in number of characters which is not necessarily the same as the number of bytes (like in UTF-8 where most characters are encoded in more than one byte), nor the number of glyphs/graphemes (some of which ...

There are three keywords that act as access specifiers. These limit the access to class members following the specifier, until another specifier changes the access level again: KeywordDescriptionpublicEveryone has accessprotectedOnly the class itself, derived classes and friends have accessprivate...

Classes/structs can have inheritance relations. If a class/struct B inherits from a class/struct A, this means that B has as a parent A. We say that B is a derived class/struct from A, and A is the base class/struct. struct A { public: int p1; protected: int p2; private: int p3;...

When using inheritance, you can specify the virtual keyword: struct A{}; struct B: public virtual A{}; When class B has virtual base A it means that A will reside in most derived class of inheritance tree, and thus that most derived class is also responsible for initializing that virtual base: ...

Aside from single inheritance: class A {}; class B : public A {}; You can also have multiple inheritance: class A {}; class B {}; class C : public A, public B {}; C will now have inherit from A and B at the same time. Note: this can lead to ambiguity if the same names are used in multipl...

The class template std::shared_ptr defines a shared pointer that is able to share ownership of an object with other shared pointers. This contrasts to std::unique_ptr which represents exclusive ownership. The sharing behavior is implemented through a technique known as reference counting, where the...

Instances of std::weak_ptr can point to objects owned by instances of std::shared_ptr while only becoming temporary owners themselves. This means that weak pointers do not alter the object's reference count and therefore do not prevent an object's deletion if all of the object's shared pointers are ...

Function overloading is having multiple functions declared in the same scope with the exact same name exist in the same place (known as scope) differing only in their signature, meaning the arguments they accept. Suppose you are writing a series of functions for generalized printing capabilities, b...

Appending an element at the end of a vector (by copying/moving): struct Point { double x, y; Point(double x, double y) : x(x), y(y) {} }; std::vector<Point> v; Point p(10.0, 2.0); v.push_back(p); // p is copied into the vector. C++11 Appending an element at the end of a vector ...

You can iterate over a std::vector in several ways. For each of the following sections, v is defined as follows: std::vector<int> v; Iterating in the Forward Direction C++11 // Range based for for(const auto& value: v) { std::cout << value << "\n"; } /...

To get started with the jQuery UI library, you'll need to add the jQuery script, the jQuery UI script, and the jQuery UI stylesheet to your HTML. First, download jQuery UI; choose the features you need on the download page. Unzip your download, and put jquery-ui.css and jquery-ui.js (and jquery.js)...

When you make a label and set its text to be more than a single line that it can display, it will be truncated and you will see only one line of text ending with three dots (...). This is because a property called numberOfLines is set to 1, and therefore only one line will be displayed. It is a comm...

You can use the nil coalescing operator to unwrap a value if it is non-nil, otherwise provide a different value: func fallbackIfNil(str: String?) -> String { return str ?? "Fallback String" } print(fallbackIfNil("Hi")) // Prints "Hi" print(fallbackIfNil(nil)...

Iterators are Positions Iterators are a means of navigating and operating on a sequence of elements and are a generalized extension of pointers. Conceptually it is important to remember that iterators are positions, not elements. For example, take the following sequence: A B C The sequence co...