Tutorial by Examples: is

Perl interpolates variable names: my $name = 'Paul'; print "Hello, $name!\n"; # Hello, Paul! my @char = ('a', 'b', 'c'); print "$char[1]\n"; # b my %map = (a => 125, b => 1080, c => 11); print "$map{a}\n"; # 125 Arrays may be interpolated as a whol...

To check if an element with a specified key exits in a WeakMap, use the .has() method. It returns true if it exits, and otherwise false. const obj1 = {}, obj2 = {}; const weakmap = new WeakMap([[obj1, 7]]); console.log(weakmap.has(obj1)); // true console.log(weakmap.has(obj2)); // false...

null returns True if there are no elements a in a foldable structure t a, and False if there is one or more. Structures for which null is True have a length of 0. ghci> null [] True ghci> null [14, 29] False ghci> null Nothing True ghci> null (Right 'a') False ghci> null ('x'...

To check if a value exits in a WeakSet, use the .has() method. const obj1 = {}, obj2 = {}; const weakset = new WeakSet([obj1]); console.log(weakset.has(obj1)); // true console.log(weakset.has(obj2)); // false

Warning! Apply shadows sparingly! Applying shadowing is expensive and is multiplicatively expensive if you apply shadowing inside an animation loop. Instead, cache a shadowed version of your image (or other drawing): At the start of your app, create a shadowed version of your image in a secon...

The traditional use of shadowing is to give 2-dimensional drawings the illusion of 3D depth. This example shows the same "button" with and without shadowing var canvas=document.createElement("canvas"); var ctx=canvas.getContext("2d"); document.body.appendChild(can...

Example of setting the isolation level: SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED; SELECT * FROM Products WHERE ProductId=1; SET TRANSACTION ISOLATION LEVEL REPEATABLE READ; --return to the default one READ UNCOMMITTED - means that a query in the current transaction can't access the...

To achieve the simplest task in Entity Framework - to connect to an existing database ExampleDatabase on your local instance of MSSQL you have to implement two classes only. First is the entity class, that will be mapped to our database table dbo.People. class Person { public int...

Creating a temporal table with a default history table is a convenient option when you want to control naming and still rely on system to create history table with default configuration. In the example below, a new system-versioned memory-optimized temporal table linked to a new disk-based history t...

The ng-list directive is used to convert a delimited string from a text input to an array of strings or vice versa. The ng-list directive uses a default delimiter of ", " (comma space). You can set the delimiter manually by assigning ng-list a delimeter like this ng-list="; ". ...

This can be done with a bit of modification in the above regex ^(?=.{10,}$)(?=(?:.*?[A-Z]){2})(?=.*?[a-z])(?=(?:.*?[0-9]){2}).*$ or ^(?=.{10,}$)(?=(?:.*[A-Z]){2})(?=.*[a-z])(?=(?:.*[0-9]){2}).* Let's see how a simple regex ^(?=(?:.*?[A-Z]){2}) works on string abcAdefD Image Credit :- ht...

C++17 The [[nodiscard]] attribute can be used to indicate that the return value of a function shouldn't be ignored when you do a function call. If the return value is ignored, the compiler should give a warning on this. The attribute can be added to: A function definition A type Adding the a...

From dataframe: mtrdd <- createDataFrame(sqlContext, mtcars) From csv: For csv's, you need to add the csv package to the environment before initiating the Spark context: Sys.setenv('SPARKR_SUBMIT_ARGS'='"--packages" "com.databricks:spark-csv_2.10:1.4.0" "sparkr-shel...

Use list() to quick assign a list of variable values into an array. See also compact() // Assigns to $a, $b and $c the values of their respective array elements in $array with keys numbered from zero list($a, $b, $c) = $array; With PHP 7.1 (currently in beta) you will be able to use s...

FOREIGN KEY constraint can be added on existing tables that are still not in relationship. Imagine that we have Company and Employee tables where Employee table CompanyId column but don't have foreign key relationship. ALTER TABLE statement enables you to add foreign key constraint on an existing c...

FOREIGN KEY columns with constraint can be added on existing tables that are still not in relationship. Imagine that we have Company and Employee tables where Employee table don't have CompanyId column. ALTER TABLE statement enables you to add new column with foreign key constraint that references ...

Polymorphism is the ability to present the same interface for different underlying implementations. The ability to implement interfaces allows completely decoupling the application logic from the UI, or from the database, or from this or that worksheet. Say you have an ISomeView interface that the...

>>> import os >>> os.stat(path_to_file).st_size == 0 or >>> import os >>> os.path.getsize(path_to_file) > 0 However, both will throw an exception if the file does not exist. To avoid having to catch such an error, do this: import os def is_empty_...

If you're using an icon to add some extra decoration or branding, it does not need to be announced to users as they are navigating your site or app aurally. Additionally, if you're using an icon to visually re-emphasize or add styling to content already present in your HTML, it does not need to be r...

Right click on the solution, Add new project From the Test section, select an Unit Test Project Pick a name for the assembly - if you are testing project Foo, the name can be Foo.Tests Add a reference to the tested project in the unit test project references