Tutorial by Examples: u

Lazy evaluation means Haskell will evaluate only list items whose values are needed. The basic recursive definition is: f (0) <- 0 f (1) <- 1 f (n) <- f (n-1) + f (n-2) If evaluated directly, it will be very slow. But, imagine we have a list that records all the results, fibs ...

The R-Logo is a multilayer raster file (red, green, blue) library(raster) r <- stack("C:/Program Files/R/R-3.2.3/doc/html/logo.jpg") plot(r) The individual layers of the RasterStack object can be adressed by [[. plot(r[[1]])

There is no simple way to obtain attributes from an interface, since classes does not inherit attributes from an interface. Whenever implementing an interface or overriding members in a derived class, you need to re-declare the attributes. So in the example below output would be True in all three c...

with clause is used to combine matching clauses. It looks like we combine anonymous functions or handle function with multiple bodies (matching clauses). Consider the case: we create a user, insert it into DB, then create greet email and then send it to the user. Without the with clause we might ...

Query: SELECT * FROM Customers ORDER BY CustomerID LIMIT 3; Result: CustomerID CustomerName ContactName Address City PostalCode Country 1 Alfreds Futterkiste Maria Anders Obere Str. 57 Berlin 12209 Ge...

In this example our project name is "helloworld" which was created with stack new helloworld simple First we have to build the project with stack build and then we can run it with stack exec helloworld-exe

The code below implements a very simple complex number type for which the underlying field is automatically promoted, following the language's type promotion rules, under application of the four basic operators (+, -, *, and /) with a member of a different field (be it another complex<T> or so...

To take a photo, first we need to declare required permissions in AndroidManifest.xml. We need two permissions: Camera - to open camera app. If attribute required is set to true you will not be able to install this app if you don't have hardware camera. WRITE_EXTERNAL_STORAGE - This permission i...

You will have to inject $filter: angular .module('filters', []) .filter('percentage', function($filter) { return function (input) { return $filter('number')(input * 100) + ' %'; }; });

ng-include allows you to delegate the control of one part of the page to a specific controller. You may want to do this because the complexity of that component is becoming such that you want to encapsulate all the logic in a dedicated controller. An example is: <div ng-include src=&q...

def foo(li=[]): li.append(1) print(li) foo([2]) # Out: [2, 1] foo([3]) # Out: [3, 1] This code behaves as expected, but what if we don't pass an argument? foo() # Out: [1] As expected... foo() # Out: [1, 1] Not as expected... This is because default arguments of function...

Consider the case of creating a nested list structure by multiplying: li = [[]] * 3 print(li) # Out: [[], [], []] At first glance we would think we have a list of containing 3 different nested lists. Let's try to append 1 to the first one: li[0].append(1) print(li) # Out: [[1], [1], [1]] ...

Looping via recursion is also possible in Kotlin as in most programming languages. fun factorial(n: Long): Long = if (n == 0) 1 else n * factorial(n - 1) println(factorial(10)) // 3628800 In the example above, the factorial function will be called repeatedly by itself until the given conditio...

The Kotlin Standard Library also provides numerous useful functions to iteratively work upon collections. For example, the map function can be used to transform a list of items. val numbers = listOf(1, 2, 3, 4, 5, 6, 7, 8, 9, 0) val numberStrings = numbers.map { "Number $it" } One of...

Use Conditionals via (syntax is in [brackets]): when [when:] Task: - name: run if operating system is debian command: echo "I am a Debian Computer" when: ansible_os_family == "Debian" loops [with_items:] loops [with_dicts:] Custom Facts [ wh...

- name: copy ssl key/cert/ssl_include files copy: src=files/ssl/{{ item }} dest=/etc/apache2/ssl/ with_items: - g_chain.crt - server.crt - server.key - ssl_vhost.inc

A simple query that selects all users from the #__users table with a username that matches John $db = JFactory::getDbo(); $query = $db->getQuery(true); $query->select('*'); $query->from('#__users'); $query->where('username = '. $db->q('John')); $db->setQuery($query); ...

Directives can be used to build reusable components. Here is an example of a "user box" component: userBox.js angular.module('simpleDirective', []).directive('userBox', function() { return { scope: { username: '=username', reputation: '=reputation' }, ...

The angular.noop is a function that performs no operations, you pass angular.noop when you need to provide a function argument that will do nothing. angular.noop() A common use for angular.noop can be to provide an empty callback to a function that will otherwise throw an error when something ...

The angular.isObject return true if and only if the argument passed to it is an object, this function will also return true for an Array and will return false for null even though typeof null is object . angular.isObject(value) This function is useful for type checking when you need a defined ...