Tutorial by Examples: n

These examples assume that you already know what Java 7's NIO is in general, and you are used to writing code using java.io.File. Use these examples as a means to quickly find more NIO-centric documentation for migrating. There is much more to Java 7's NIO such as memory-mapped files or opening a Z...

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...

By default, user input history in IEx do not persist across different sessions. erlang-history adds history support to both the Erlang shell and IEx: git clone [email protected]:ferd/erlang-history.git cd erlang-history sudo make install You can now access your previous inputs using the up and d...

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 we need to do the sum of each column in a dataset set.seed(20) df1 <- data.frame(ID = rep(c("A", "B", "C"), each = 3), V1 = rnorm(9), V2 = rnorm(9)) m1 <- as.matrix(df1[-1]) There are many ways to do this. Using base R, the best option would be col...

A common question is "I have a value of IO a, but I want to do something to that a value: how do I get access to it?" How can one operate on data that comes from the outside world (for example, incrementing a number typed by the user)? The point is that if you use a pure function on data ...

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 continue keyword halts the current iteration of a loop but does not terminate the loop. Just like the break statement the continue statement is situated inside the loop body. When executed, the continue statement causes execution to immediately jump to the loop conditional. In the followin...

Accepts a mathematical expression and returns a numerical value. It is especially useful when working with different types of units (e.g. subtracting a px value from a percentage) to calculate the value of an attribute. +, -, /, and * operators can all be used, and parentheses can be added to spec...

Returns the value of an attribute of the selected element. Below is a blockquote element which contains a character inside a data-* attribute which CSS can use (e.g. inside the ::before and ::after pseudo-element) using this function. <blockquote data-mark='"'></blockquote> 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 ...

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 ...

A session is usually obtained using sessionmaker, which creates a Session class unique to your application. Most commonly, the Session class is bound to an engine, allowing instances to use the engine implicitly. from sqlalchemy.orm import sessionmaker # Initial configuration arguments Session ...