Tutorial by Examples: re

The map function is the simplest one among Python built-ins used for functional programming. map() applies a specified function to each element in an iterable: names = ['Fred', 'Wilma', 'Barney'] Python 3.x3.0 map(len, names) # map in Python 3.x is a class; its instances are iterable # Out: &...

The remainder / modulus operator (%) returns the remainder after (integer) division. console.log( 42 % 10); // 2 console.log( 42 % -10); // 2 console.log(-42 % 10); // -2 console.log(-42 % -10); // -2 console.log(-40 % 10); // -0 console.log( 40 % 10); // 0 This operator returns th...

The Increment operator (++) increments its operand by one. If used as a postfix, then it returns the value before incrementing. If used as a prefix, then it returns the value after incrementing. //postfix var a = 5, // 5 b = a++, // 5 c = a // 6 In this case, a is incr...

The decrement operator (--) decrements numbers by one. If used as a postfix to n, the operator returns the current n and then assigns the decremented the value. If used as a prefix to n, the operator assigns the decremented n and then returns the changed value. var a = 5, // 5 b = a...

Given a list comprehension you can append one or more if conditions to filter values. [<expression> for <element> in <iterable> if <condition>] For each <element> in <iterable>; if <condition> evaluates to True, add <expression> (usually a function...

print_r() - Outputting Arrays and Objects for debugging print_r will output a human readable format of an array or object. You may have a variable that is an array or object. Trying to output it with an echo will throw the error: Notice: Array to string conversion. You can instead use the print_r...

Variables can be incremented or decremented by 1 using the ++ and -- operators, respectively. When the ++ and -- operators follow variables, they are called post-increment and post-decrement respectively. int a = 10; a++; // a now equals 11 a--; // a now equals 10 again When the ++ and -- ope...

The exit construct can be used to pass a return code to the executing environment. #!/usr/bin/php if ($argv[1] === "bad") { exit(1); } else { exit(0); } By default an exit code of 0 will be returned if none is provided, i.e. exit is the same as exit(0). As exit is not a ...

When both operands are numeric, they are compared normally: 1 < 2 // true 2 <= 2 // true 3 >= 5 // false true < false // false (implicitly converted to numbers, 1 > 0) When both operands are strings, they are compared lexicographically (according to alphabeti...

At the command line, first verify that you have Git installed: On all operating systems: git --version On UNIX-like operating systems: which git If nothing is returned, or the command is not recognized, you may have to install Git on your system by downloading and running the installer. See...

The git clone command is used to copy an existing Git repository from a server to the local machine. For example, to clone a GitHub project: cd <path where you'd like the clone to create a directory> git clone https://github.com/username/projectname.git To clone a BitBucket project: cd ...

Normally, enums can't be recursive (because they would require infinite storage): enum Tree<T> { case leaf(T) case branch(Tree<T>, Tree<T>) // error: recursive enum 'Tree<T>' is not marked 'indirect' } The indirect keyword makes the enum store its payload with...

This example assumes Ruby and Ruby on Rails have already been installed properly. If not, you can find how to do it here. Open up a command line or terminal. To generate a new rails application, use rails new command followed by the name of your application: $ rails new my_app If you want to c...

Breaking out of a while loop var i = 0; while(true) { i++; if(i === 42) { break; } } console.log(i); Expected output: 42 Breaking out of a for loop var i; for(i = 0; i < 100; i++) { if(i === 42) { break; } } console.log(i); Expected o...

Functions can return a value that you can use directly: def give_me_five(): return 5 print(give_me_five()) # Print the returned value # Out: 5 or save the value for later use: num = give_me_five() print(num) # Print the saved returned value # Out: 5 or use the value f...

The math module contains the math.sqrt()-function that can compute the square root of any number (that can be converted to a float) and the result will always be a float: import math math.sqrt(9) # 3.0 math.sqrt(11.11) # 3.3331666624997918 math.sqrt(Decimal('6.25')) ...

Sometimes you don't want to have your function accessible/stored as a variable. You can create an Immediately Invoked Function Expression (IIFE for short). These are essentially self-executing anonymous functions. They have access to the surrounding scope, but the function itself and any internal va...

import random randint() Returns a random integer between x and y (inclusive): random.randint(x, y) For example getting a random number between 1 and 8: random.randint(1, 8) # Out: 8 randrange() random.randrange has the same syntax as range and unlike random.randint, the last value is no...

git log will display all your commits with the author and hash. This will be shown over multiple lines per commit. (If you wish to show a single line per commit, look at onelineing). Use the q key to exit the log. By default, with no arguments, git log lists the commits made in that reposito...

Protocols may define associated type requirements using the associatedtype keyword: protocol Container { associatedtype Element var count: Int { get } subscript(index: Int) -> Element { get set } } Protocols with associated type requirements can only be used as generic constraints:...