Tutorial by Examples: d

You should have Elm platform installed on your computer, the following tutorial is written with the assumption, that you are familiar with terminal. Initialization Create a folder and navigate to it with your terminal: $ mkdir elm-app $ cd elm-app/ Initialize Elm project and install core depe...

A distinctive syntactic peculiarity of C is that declarations mirror the use of the declared object as it would be in a normal expression. The following set of operators with identical precedence and associativity are reused in declarators, namely: the unary * "dereference" operator wh...

git diff HEAD^ HEAD This will show the changes between the previous commit and the current commit.

instance Monoid [a] where mempty = [] mappend = (++) Checking the Monoid laws for this instance: mempty `mappend` x = x <-> [] ++ xs = xs -- prepending an empty list is a no-op x `mappend` mempty = x <-> xs ++ [] = xs -- appending an empty list is a no-op x...

mconcat :: [a] -> a is another method of the Monoid typeclass: ghci> mconcat [Sum 1, Sum 2, Sum 3] Sum {getSum = 6} ghci> mconcat ["concat", "enate"] "concatenate" Its default definition is mconcat = foldr mappend mempty.

In the following examples, we'll be using the following samples: List<Product> Products = new List<Product>() { new Product() { ProductId = 1, Name = "Book nr 1", Price = 25 }, new Product() { ProductId = 2, Name = "Book nr 2&quot...

Numbers are monoidal in two ways: addition with 0 as the unit, and multiplication with 1 as the unit. Both are equally valid and useful in different circumstances. So rather than choose a preferred instance for numbers, there are two newtypes, Sum and Product to tag them for the different functional...

Wikipedia currently defines a pure function as follows: The function always evaluates the same result value given the same argument value(s). The function result value cannot depend on any hidden information or state that may change while program execution proceeds or between different executions...

Suppose you have this type: data Person = Person { name :: String, age:: Int } deriving (Show, Eq) and two values: alex = Person { name = "Alex", age = 21 } jenny = Person { name = "Jenny", age = 36 } a new value of type Person can be created by copying from alex, specif...

import pandas as pd # Save dataframe to pickled pandas object df.to_pickle(file_name) # where to save it usually as a .plk # Load dataframe from pickled pandas object df= pd.read_pickle(file_name)

The do...while statement will execute a block of code at least once - it then will repeat the loop as long as a condition is true. The following example will increment the value of $i at least once, and it will continue incrementing the variable $i as long as it has a value of less than 25; $i...

Find single record based on id. $model = User::findOne($id); Select single column based on id. $model = User::findOne($id)->name; Retrieve the single record from the database based on condition. $model = User::find()->one(); // give first record $model = User::find()->where(['i...

Using scenario you can perform validation on different situation Define scenario in model class class User extends \yii\db\ActiveRecord { public static function tableName() { return 'user_master'; } // define validation in rule() function public ...

Vector based graphics are represented by a plethora of data that must be computed by the CPU (vector points, arcs, colors, etc). Anything other than simple shapes with minimal points and straight lines will consume vast amounts of CPU resource. There is a "Cache as Bitmap" flag that can b...

Using the Vector.<T> type and the for each loop is more performant than a conventional array and for loop: Good: var list:Vector.<Sprite> = new <Sprite>[]; for each(var sprite:Sprite in list) { sprite.x += 1; } Bad: var list:Array = []; for (var i:int = 0; i < ...

Steps to Create component: Create a folder named components in your project root folder Create your component inside components folder e.g.: MyComponent.php namespace app\components; use Yii; use yii\base\Component; use yii\base\InvalidConfigException; class MyComponent ...

Create function in MyComponent.php namespace app\components; use Yii; use yii\base\Component; use yii\base\InvalidConfigException; use yii\helpers\Url; use yii\helpers\ArrayHelper; use app\models\User; class MyComponent extends Component ...

New or detached objects may be added to the session using add(): session.add(obj) A sequence of objects may be added using add_all(): session.add_all([obj1, obj2, obj3]) An INSERT will be emitted to the database during the next flush, which happens automatically. Changes are persisted when t...

To delete persisted objects use delete(): session.delete(obj) Actual deletion from the database will happen on next flush.

There are many ways find the location of a value in an array. The following example snippets all assume that the array is one of the following: String[] strings = new String[] { "A", "B", "C" }; int[] ints = new int[] { 1, 2, 3, 4 }; In addition, each one sets...