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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 for statement is used when you know how many times you want to execute a statement or a block of statements. The initializer is used to set the start value for the counter of the number of loop iterations. A variable may be declared here for this purpose and it is traditional to name it $i....

The foreach statement is used to loop through arrays. For each iteration the value of the current array element is assigned to $value variable and the array pointer is moved by one and in the next iteration next element will be processed. The following example displays the items in the array a...

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...

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 ...

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 < ...

If you do not require an array to be in any particular order, a little trick with pop() will afford you enormous performance gains compared to splice(). When you splice() an array, the index of subsequent elements in that array needs to be reduced by 1. This process can consume a large chunk of tim...

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 ...