Tutorial by Examples: u

The (?(DEFINE)...) construct lets you define subpatterns you may reference later through recursion. When encountered in the pattern it will not be matched against. This group should contain named subpattern definitions, which will be accessible only through recursion. You can define grammars this w...

Subpatterns can be referenced with their relative group number: (?-1) will recurse into the previous group (?+1) will recurse into the next group Also usable with the \g<N> syntax.

To pass data from the current view controller back to the previous view controller, you can use the delegate pattern. This example assumes that you have made a segue in the Interface Builder and that you set the segue identifier to showSecondViewController. The outlets and actions must also be ho...

You can create a horizontal break to divide your text by placing three (or more) underscores ___ or asterisks *** or hyphens --- on their own line. You can create a horizontal break to divide your text by placing three (or more) underscores or asterisks or hyphens o...

Generators can be used to represent infinite sequences: def integers_starting_from(n): while True: yield n n += 1 natural_numbers = integers_starting_from(1) Infinite sequence of numbers as above can also be generated with the help of itertools.count. The above code cou...

The built-in function len returns the number of elements in a map m := map[string]int{} len(m) // 0 m["foo"] = 1 len(m) // 1 If a variable points to a nil map, then len returns 0. var m map[string]int len(m) // 0

Given the flavors, the named capture group may looks like this: (?'name'X) (?<name>X) (?P<name>X) With X being the pattern you want to capture. Let's consider the following string: Once upon a time there was a pretty little girl... Once upon a time there was a unicorn with an h...

As you may (or not) know, you can reference a capture group with: $1 1 being the group number. In the same way, you can reference a named capture group with: ${name} \{name} g\{name} Let's take the preceding example and replace the matches with The hero of the story is a ${subject}. T...

In a normal string, the backslash character is the escape character, which instructs the compiler to look at the next character(s) to determine the actual character in the string. (Full list of character escapes) In verbatim strings, there are no character escapes (except for "" which is ...

In functions taking callable as an argument, you can also put a string with PHP built-in function. It's common to use trim as array_map parameter to remove leading and trailing whitespace from all strings in the array. $arr = [' one ', 'two ', ' three']; var_dump(array_map('trim', $arr)); ...

To parse lots of parameters, the prefered way of doing this is using a while loop, a case statement, and shift. shift is used to pop the first parameter in the series, making what used to be $2, now be $1. This is useful for processing arguments one at a time. #!/bin/bash # Load the user define...

These behave in the same manner as nested subqueries but with a different syntax. WITH ReadyCars AS ( SELECT * FROM Cars WHERE Status = 'READY' ) SELECT ID, Model, TotalCost FROM ReadyCars ORDER BY TotalCost; IDModelTotalCost1Ford F-1502002Ford F-150230 Equivalent subquery syntax ...

WITH RECURSIVE ManagersOfJonathon AS ( -- start with this row SELECT * FROM Employees WHERE ID = 4 UNION ALL -- get manager(s) of all previously selected rows SELECT Employees.* FROM Employees JOIN ManagersOfJonathon ON Employees.ID = Manager...

Most databases do not have a native way of generating a series of numbers for ad-hoc use; however, common table expressions can be used with recursion to emulate that type of function. The following example generates a common table expression called Numbers with a column i which has a row for numbe...

WITH RECURSIVE ManagedByJames(Level, ID, FName, LName) AS ( -- start with this row SELECT 1, ID, FName, LName FROM Employees WHERE ID = 1 UNION ALL -- get employees that have any of the previously selected rows as manager SELECT ManagedByJames.Level + 1, ...

BuildConfigField Gradle allows buildConfigField lines to define constants. These constants will be accessible at runtime as static fields of the BuildConfig class. This can be used to create flavors by defining all fields within the defaultConfig block, then overriding them for individual build fla...

# Create the nodes # In a real world scenario we would use at least 3 managers to cover the fail of one manager. docker-machine create -d virtualbox manager docker-machine create -d virtualbox worker1 # Create the swarm # It is possible to define a port for the *advertise-addr* and *listen-ad...

There is a collection in .Net used to manage values in a Queue that uses the FIFO (first-in first-out) concept. The basics of queues is the method Enqueue(T item) which is used to add elements in the queue and Dequeue() which is used to get the first element and remove it from the queue. The generic...

public struct Vector { public int X; public int Y; public int Z; } public struct Point { public decimal x, y; public Point(decimal pointX, decimal pointY) { x = pointX; y = pointY; } } struct instance fields can be set via a p...

Assuming the following Person class: public class Person { public string Name { get; set; } public int Age { get; set; } } The following lambda: p => p.Age > 18 Can be passed as an argument to both methods: public void AsFunc(Func<Person, bool> func) public void AsE...