Tutorial by Examples: p

slice = append(slice, "hello", "world")

When two margins are touching each other vertically, they are collapsed. When two margins touch horizontally, they do not collapse. Example of adjacent vertical margins: Consider the following styles and markup: div{ margin: 10px; } <div> some content </div> <div&gt...

We can illustrate this problem with the following pseudo-code function foo() { global $bob; $bob->doSomething(); } Your first question here is an obvious one Where did $bob come from? Are you confused? Good. You've just learned why globals are confusing and considered a bad p...

The prefix ! operator returns the logical negation of its argument. That is, !true returns false, and !false returns true. print(!true) // prints "false" print(!false) // prints "true" func test(_ someBoolean: Bool) { if !someBoolean { print("someBoolean ...

Table cells can span multiple columns or rows using the colspan and rowspan attributes. These attributes can be applied to <th> and <td> elements. <table> <tr> <td>row 1 col 1</td> <td>row 1 col 2</td> <td>row 1 c...

You can "overwrite" a language declaration: <p lang="en">This English sentence contains the German word <span lang="de">Hallo</span>.</p>

params allows a method parameter to receive a variable number of arguments, i.e. zero, one or multiple arguments are allowed for that parameter. static int AddAll(params int[] numbers) { int total = 0; foreach (int number in numbers) { total += number; } ret...

Object initializers are handy when you need to create an object and set a couple of properties right away, but the available constructors are not sufficient. Say you have a class public class Book { public string Title { get; set; } public string Author { get; set; } // the rest o...

Object initializers are the only way to initialize anonymous types, which are types generated by the compiler. var album = new { Band = "Beatles", Title = "Abbey Road" }; For that reason object initializers are widely used in LINQ select queries, since they provide a convenie...

The construct (?R) is equivalent to (?0) (or \g<0>) - it lets you recurse the whole pattern: <(?>[^<>]+|(?R))+> This will match properly balanced angle brackets with any text in-between the brackets, like <a<b>c<d>e>.

You can recurse into a subpattern using the following constructs (depending on the flavor), assuming n is a capturing group number, and name the name of a capturing group. (?n) \g<n> \g'0' (?&name) \g<name> \g'name' (?P>name) The following pattern: \[(?<angle>&...

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...

Documentation comments are placed directly above the method or class they describe. They begin with three forward slashes ///, and allow meta information to be stored via XML. /// <summary> /// Bar method description /// </summary> public void Bar() { } Information in...

import re precompiled_pattern = re.compile(r"(\d+)") matches = precompiled_pattern.search("The answer is 41!") matches.group(1) # Out: 41 matches = precompiled_pattern.search("Or was it 42?") matches.group(1) # Out: 42 Compiling a pattern allows it to be r...

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 ...