Tutorial by Examples: n

The easiest way to consume a successful Future-- or rather, get the value inside the Future-- is to use the map method. Suppose some code calls the divide method of the FutureDivider object from the "Creating a Future" example. What would the code need to look like to get the quotient of...

Sometimes the computation in a Future can create an exception, which will cause the Future to fail. In the "Creating a Future" example, what if the calling code passed 55 and 0 to the divide method? It'd throw an ArithmeticException after trying to divide by zero, of course. How would t...

The previous examples demonstrated the individual features of a Future, handling success and failure cases. Usually, however, both features are handled much more tersely. Here's the example, written in a neater and more realistic way: object Calculator { def calculateAndReport(a: Int, b: Int...

To convert exceptions into Either or Option types, you can use methods that provided in scala.util.control.Exception import scala.util.control.Exception._ val plain = "71a" val optionInt: Option[Int] = catching(classOf[java.lang.NumberFormatException]) opt { plain.toInt } val eitherI...

A very interesting type of JOIN is the LATERAL JOIN (new in PostgreSQL 9.3+), which is also known as CROSS APPLY/OUTER APPLY in SQL-Server & Oracle. The basic idea is that a table-valued function (or inline subquery) gets applied for every row you join. This makes it possible to, for example...

One type of JOIN that is less known, is the FULL JOIN. (Note: FULL JOIN is not supported by MySQL as per 2016) A FULL OUTER JOIN returns all rows from the left table, and all rows from the right table. If there are rows in the left table that do not have matches in the right table, or if there a...

Recursive joins are often used to obtain parent-child data. In SQL, they are implemented with recursive common table expressions, for example: WITH RECURSIVE MyDescendants AS ( SELECT Name FROM People WHERE Name = 'John Doe' UNION ALL SELECT People.Name FROM Peopl...

If you implement a text-search as LIKE-query, you usually do it like this: SELECT * FROM T_Whatever WHERE SomeField LIKE CONCAT('%', @in_SearchText, '%') However, (apart from the fact that you shouldn't necessarely use LIKE when you can use fulltext-search) this creates a problem when someb...

Over the course of time B-Tree indexes may become fragmented because of updating/deleting/inserting data. In SQLServer terminology we can have internal (index page which is half empty ) and external (logical page order doesn't correspond physical order). Rebuilding index is very similar to dropping...

You can override the default vmoptions with your own personal settings by choosing Help > Edit Custom VM Options from the Android Studio toolbar. This will create a local copy which you are free to edit. Alternatively, you can edit the default vmoptions directly using the paths given below. Note...

If your array or array-like object is numeric, that is, if all its elements are numbers, then you can use Math.min.apply or Math.max.apply by passing null as the first argument, and your array as the second. var myArray = [1, 2, 3, 4]; Math.min.apply(null, myArray); // 1 Math.max.apply(null, my...

To read default configuration properties: package com.example; public class ExampleApplication { private Properties getDefaults() throws IOException { Properties defaults = new Properties(); try (InputStream defaultsStream = ExampleApplication.class.getResou...

SOAP services can publish metadata that describes the methods that may be invoked by clients. Clients can use tools such as Visual Studio to automatically generate code (known as client proxies). The proxies hide the complexity of invoking a service. To invoke a service, one merely invokes a metho...

To find the largest or smallest element stored in a vector, you can use the methods std::max_element and std::min_element, respectively. These methods are defined in <algorithm> header. If several elements are equivalent to the greatest (smallest) element, the methods return the iterator to th...

View components encapsulate reusable pieces of logic and views. They are defined by: A ViewComponent class containing the logic for fetching and preparing the data for the view and deciding which view to render. One or more views Since they contain logic, they are more flexible than partial v...

The default project template creates a partial view _LoginPartial.cshtml which contains a bit of logic for finding out whether the user is logged in or not and find out its user name. Since a view component might be a better fit (as there is logic involved and even 2 services injected) the followin...

Move a rectangle 10 units to the right and 20 units down: <svg xmlns="http://www.w3.org/2000/svg"> <rect x="0" y="0" width="30" height="30" transform="translate(10, 20)" /> </svg> Move it 0 units horizontally and...

Transformations can be concatenated and are applied right to left Rotate a rectangle by 90 degrees and then move it down by 20 units and to the right by 20 units: <svg xmlns="http://www.w3.org/2000/svg"> <rect x="-10" y="-20" width="20" height=...

<svg width="400" height="400"> <defs> <pattern id="pattern1" width="0.2" height="0.2" patternUnits="objectBoundingBox"> <circle cx="10" cy="10" r="10" fill="#0000ff" /&...

Let’s try some basic expression in the REPL: CL-USER> (+ 1 2 3) 6 CL-USER> (- 3 1 1) 1 CL-USER> (- 3) -3 CL-USER> (+ 5.3 (- 3 2) (* 2 2)) 10.3 CL-USER> (concatenate 'string "Hello, " "World!") "Hello, World!" CL-USER> The basic building ...