Tutorial by Examples: r

Structure data types are useful way to package related data and have them behave like a single variable. Declaring a simple struct that holds two int members: struct point { int x; int y; }; x and y are called the members (or fields) of point struct. Defining and using structs: ...

Trim is used to remove write-space at the beginning or end of selection In MSSQL there is no single TRIM() SELECT LTRIM(' Hello ') --returns 'Hello ' SELECT RTRIM(' Hello ') --returns ' Hello' SELECT LTRIM(RTRIM(' Hello ')) --returns 'Hello' MySql and Oracle SELECT TRIM(' Hello ') ...

SELECT UPPER('HelloWorld') --returns 'HELLOWORLD' SELECT LOWER('HelloWorld') --returns 'helloworld'

Syntax is: SUBSTRING ( string_expression, start, length ). Note that SQL strings are 1-indexed. SELECT SUBSTRING('Hello', 1, 2) --returns 'He' SELECT SUBSTRING('Hello', 3, 3) --returns 'llo' This is often used in conjunction with the LEN() function to get the last n characters of a string of un...

Detailed instructions on getting azureservicebus set up or installed.

While the Java Date class has several constructors, you'll notice that most are deprecated. The only acceptable way of creating a Date instance directly is either by using the empty constructor or passing in a long (number of milliseconds since standard base time). Neither are handy unless you're lo...

We can provide a consumer that will be called with the multiple relevant values: C++11 template <class F> void foo(int a, int b, F consumer) { consumer(a + b, a - b, a * b, a / b); } // use is simple... ignoring some results is possible as well foo(5, 12, [](int sum, int , int , i...

// The Option type can either contain Some value or None. fn find(value: i32, slice: &[i32]) -> Option<usize> { for (index, &element) in slice.iter().enumerate() { if element == value { // Return a value (wrapped in Some). return Some(index);...

Inject and reduce are different names for the same thing. In other languages these functions are often called folds (like foldl or foldr). These methods are available on every Enumerable object. Inject takes a two argument function and applies that to all of the pairs of elements in the Array. For...

Discriminated unions in F# offer a a way to define types which may hold any number of different data types. Their functionality is similar to C++ unions or VB variants, but with the additional benefit of being type safe. // define a discriminated union that can hold either a float or a string type...

To apply a function to every item in an array, use array_map(). This will return a new array. $array = array(1,2,3,4,5); //each array item is iterated over and gets stored in the function parameter. $newArray = array_map(function($item) { return $item + 1; }, $array); $newArray now is a...

Here is an example of a service that greets people by the given name, and keeps track of how many users it encountered. See usage below. %% greeter.erl %% Greets people and counts number of times it did so. -module(greeter). -behaviour(gen_server). %% Export API Functions -export([start_link/0...

It is possible to release dynamically allocated memory by calling free(). int *p = malloc(10 * sizeof *p); /* allocation of memory */ if (p == NULL) { perror("malloc failed"); return -1; } free(p); /* release of memory */ /* note that after free(p), even using the *value...

Standard Allocation The C dynamic memory allocation functions are defined in the <stdlib.h> header. If one wishes to allocate memory space for an object dynamically, the following code can be used: int *p = malloc(10 * sizeof *p); if (p == NULL) { perror("malloc() failed");...

In PHP, a fatal error is a kind of error that cannot be caught, that is, after experiencing a fatal error a program does not resume. However, to log this error or somehow handle the crash you can use register_shutdown_function to register shutdown handler. function fatalErrorHandler() { // Let...

If the variable contains a value of an immutable type (e.g. a string) then it is okay to assign a default value like this class Rectangle(object): def __init__(self, width, height, color='blue'): self.width = width self.height = height self.color = color d...

In Erlang, numbers are either integers or floats. Erlang uses arbitrary-precision for integers (bignums), so their values are limited only by the memory size of your system. 1> 11. 11 2> -44. -44 3> 0.1. 0.1 4> 5.1e-3. 0.0051 5> 5.2e2. 520.0 Numbers can be used in various...

A binary is a sequence of unsigned 8-bit bytes. 1> <<1,2,3,255>>. <<1,2,3,255>> 2> <<256,257,258>>. <<0,1,2>> 3> <<"hello","world">>. <<"helloworld">> A bitstring is a generalized ...

XSLT is a special-purpose programming language; it is widely used for transforming XML documents either into a different XML format, into HTML, or into text-based formats. There are two main versions of XSLT in use: XSLT 1.0 and XSLT 2.0. XSLT 1.0 is more widely implemented but has many restriction...

Migrations in a Laravel 5 application live in the database/migrations directory. Their filenames conform to a particular format: <year>_<month>_<day>_<hour><minute><second>_<name>.php One migration file should represent a schema update to solve a particu...