Tutorial by Examples: u

Sometimes it can be interesting to have a cross-talk between the user and the program, one example being the swirl package that had been designed to teach R in R. One can ask for user input using the readline command: name <- readline(prompt = "What is your name?") The user can the...

Description: Evaluate expression after user's confirmation. Arguments: ng-confirm-click:(expression) Expression to evaluate when confirmed. ng-confirm-message:(template) Message to be shown in confirm dialog. Code: Directives.directive("ngConfirmClick", ["$parse","...

YAML provides a way to store structured data. The data can be a simple set of name-value pairs or a complex hierarchical data with values even being arrays. Consider the following YAML file: database: driver: mysql host: database.mydomain.com port: 3306 db_name: sample_db ...

How to use conditional execution of command lists Any builtin command, expression, or function, as well as any external command or script can be executed conditionally using the &&(and) and ||(or) operators. For example, this will only print the current directory if the cd command was succ...

First, you need to install django-debug-toolbar: pip install django-debug-toolbar settings.py: Next, include it to project's installed apps, but be careful - it's always a good practice to use a different settings.py file for such development-only apps and middlewares as debug toolbar: # If en...

def lst = ['foo', 'bar', 'baz'] lst.collect { it } // ['foo', 'bar', 'baz'] lst.collect { it.toUpperCase() } // ['FOO', 'BAR', 'BAZ'] To collect keys or values from a maps def map = [foo: 'FOO', bar: 'BAR', baz: 'BAZ'] def keys = map.collect { it.key } // ['foo', 'bar', 'baz'] def vals = m...

def lst = ['foo', 'foo', 'bar', 'baz'] // *modifies* the list removing duplicate items lst.unique() // [foo, bar, baz] // setting to false the "mutate" argument returns a new list, leaving the original intact lst.unique(false) // [foo, bar, baz] // convert the list to a Set, thu...

The Slow Query Log consists of log events for queries taking up to long_query_time seconds to finish. For instance, up to 10 seconds to complete. To see the time threshold currently set, issue the following: SELECT @@long_query_time; +-------------------+ | @@long_query_time | +-----------------...

WebRTC is an open framework for the web that enables Real Time Communications in the browser. It includes the fundamental building blocks for high-quality communications on the web, such as network, audio and video components used in voice and video chat applications. These components, when impleme...

You can start the remote debugging from Developer menu. After selecting the enable remote debugging it will open Google Chrome, So that you can log the output into your console. You can also write debugger syntax into your js code.

Polymorphism without inheritance in the form of duck typing as available in Python due to its dynamic typing system. This means that as long as the classes contain the same methods the Python interpreter does not distinguish between them, as the only checking of the calls occurs at run-time. class ...

While catching the Throwable, Exception, Error and RuntimeException exceptions is bad, throwing them is even worse. The basic problem is that when your application needs to handle exceptions, the presence of the top level exceptions make it hard to discriminate between different error conditions. ...

The following example can be used to find the total row count for a specific table in a database if table_name is replaced by the the table you wish to query: SELECT COUNT(*) AS [TotalRowCount] FROM table_name; It is also possible to get the row count for all tables by joining back to the table'...

enum Fruit { apple, banana } main() { var a = Fruit.apple; switch (a) { case Fruit.apple: print('it is an apple'); break; } // get all the values of the enums for (List<Fruit> value in Fruit.values) { print(value); } // get the second val...

First of all, ensure that you've enabled the 'Virtualization' in your BIOS setup. Start the Android SDK Manager, select Extras and then select Intel Hardware Accelerated Execution Manager and wait until your download completes. If it still doesn't work, open your SDK folder and run /extras/intel/Ha...

First define an ExitActivity in the AndroidManifest.xml <activity android:name="com.your_example_app.activities.ExitActivity" android:autoRemoveFromRecents="true" android:theme="@android:style/Theme.NoDisplay" /> Afterwards the ExitA...

Detailed instructions on getting azure-service-fabric set up or installed.

Rather than passing a static string as a predicate's criteria. It is possible to substitute values by using format specifiers. There are five format specifiers: %K is a var arg substitution for a key path. %@ is a var arg substitution for an object value-often a string, number, date, or an array...

When we are working on a framework, if the constraints are not too complex, we'd better use Interface Builder or NSLayoutConstraint in code to make it smaller enough, instead of import Masonry or SnapKit. for example: Objective-C // 1. create views UIView *blueView = [[UIView alloc...

let data = [1; 2; 3; 4; 5;] let repeating = seq {while true do yield! data} Repeating sequences can be created using a seq {} computation expression