Tutorial by Examples: r

Every format type is related to an HTML tag. The First Heading refers to the <h1> tag and is visualized like: Hello World and it's written underlining the text with =: Hello World =========== or by prepending # to the text: # Hello World The Second Heading refers to the <h2&gt...

<script src= "http://player.twitch.tv/js/embed/v1.js"></script> <div id="{PLAYER_DIV_ID}"></div> <script type="text/javascript"> var options = { width: 854, height: 480, channel: "{CHANNEL}" ...

This is an enum that is also a callable function that tests String inputs against precompiled regular expression patterns. import java.util.function.Predicate; import java.util.regex.Pattern; enum RegEx implements Predicate<String> { UPPER("[A-Z]+"), LOWER("[a-z]+&quot...

One use case for assertion is precondition and postcondition. This can be very useful to maintain invariant and design by contract. For a example a length is always zero or positive so this function must return a zero or positive value. #include <stdio.h> /* Uncomment to disable `assert()`...

In this example, we'll be looking at how to store a credit card using the PayPal vault, then reference that stored credit card to process a credit card transaction for a user. The reason why we would want to use the vault is so that we don't have to store sensitive credit card information on our ow...

The following C source file (which we will call hello.c for demonstration purposes) produces an extension module named hello that contains a single function greet(): #include <Python.h> #include <stdio.h> #if PY_MAJOR_VERSION >= 3 #define IS_PY3K #endif static PyObject *hell...

When an exception object is created (i.e. when you new it), the Throwable constructor captures information about the context in which the exception was created. Later on, this information can be output in the form of a stacktrace, which can be used to help diagnose the problem that caused the excep...

To join all of an array's elements into a string, you can use the join method: console.log(["Hello", " ", "world"].join("")); // "Hello world" console.log([1, 800, 555, 1234].join("-")); // "1-800-555-1234" As you can see in ...

SELECT 'Hello world!' FROM dual; In Oracle's flavor of SQL, "dual is just a convienence table". It was originally intended to double rows via a JOIN, but now contains one row with a DUMMY value of 'X'.

For JavaScript, here is the code we recommend for generating, persisting and retrieving a UUID. This could be wrapped in a function can called directly from the PUBNUB.init function rather than the two step inline solution below. // get/create/store UUID var UUID = PUBNUB.db.get('session') || (fun...

For Android, here is the code we recommend for generating, persisting and retrieving a UUID. There is not constructor that accepts the UUID as a parameter, so you must instantiate Pubnub object first then use the setter to provide the UUID. // creating the Pubnub connection object with minimal args...

You can overload all basic arithmetic operators: + and += - and -= * and *= / and /= & and &= | and |= ^ and ^= >> and >>= << and <<= Overloading for all operators is the same. Scroll down for explanation Overloading outside of class/struct: //operator...

You can overload the 2 unary operators: ++foo and foo++ --foo and foo-- Overloading is the same for both types (++ and --). Scroll down for explanation Overloading outside of class/struct: //Prefix operator ++foo T& operator++(T& lhs) { //Perform addition return lhs; } ...

You can overload all comparison operators: == and != > and < >= and <= The recommended way to overload all those operators is by implementing only 2 operators (== and <) and then using those to define the rest. Scroll down for explanation Overloading outside of class/struct: ...

You can overload type operators, so that your type can be implicitly converted into the specified type. The conversion operator must be defined in a class/struct: operator T() const { /* return something */ } Note: the operator is const to allow const objects to be converted. Example: struct ...

You can even overload the array subscript operator []. You should always (99.98% of the time) implement 2 versions, a const and a not-const version, because if the object is const, it should not be able to modify the object returned by []. The arguments are passed by const& instead of by value...

You can overload the function call operator (): Overloading must be done inside of a class/struct: //R -> Return type //Types -> any different type R operator()(Type name, Type2 name2, ...) { //Do something //return something } //Use it like this (R is return type, a and b a...

The assignment operator is one of the most important operators because it allows you to change the status of a variable. If you do not overload the assigment operator for your class/struct, it is automatically generated by the compiler: the automatically-generated assignment operator performs a &qu...

Overloading the bitwise NOT (~) is fairly simple. Scroll down for explanation Overloading outside of class/struct: T operator~(T lhs) { //Do operation return lhs; } Overloading inside of class/struct: T operator~() { T t(*this); //Do operation return t; } Note...

The operators << and >> are commonly used as "write" and "read" operators: std::ostream overloads << to write variables to the underlying stream (example: std::cout) std::istream overloads >> to read from the underlying stream to a variable (example: s...