Tutorial by Examples: r

In case of SQL Server 2017 or vnext we can use in-built STRING_AGG for this aggregation. For same student table, create table #yourstudent (subjectid int, studentname varchar(10)) insert into #yourstudent (subjectid, studentname) values ( 1 ,'Mary' ) ,( 1 ,'John' ) ,( 1 ...

import scalaz._ import Scalaz._ scala> val len: String => Int = _.length len: String => Int = $$Lambda$1164/969820333@7e758f40 scala> Functor[Option].map(Some("foo"))(len) res0: Option[Int] = Some(3) scala> Functor[Option].map(None)(len) res1: Option[Int] = None ...

import scalaz._ import Scalaz._ scala> val plus1 = (_: Int) + 1 plus1: Int => Int = $$Lambda$1167/1113119649@6a6bfd97 scala> val plus2 = (_: Int) + 2 plus2: Int => Int = $$Lambda$1168/924329548@6bbe050f scala> val rev = (_: String).reverse rev: String => String = $$Lambd...

Unary operators act on the object upon which they are called and have high precedence. (See Remarks) When used postfix, the action occurs only after the entire operation is evaluated, leading to some interesting arithmetics: int a = 1; ++a; // result: 2 a--; // result: 1 i...

A common need for random numbers it to generate a number that is X% of some max value. this can be done by treating the result of NextDouble() as a percentage: var rnd = new Random(); var maxValue = 5000; var percentage = rnd.NextDouble(); var result = maxValue * percentage; //suppose NextDoub...

apcu_store can be used to store, apcu_fetch to retrieve values: $key = 'Hello'; $value = 'World'; apcu_store($key, $value); print(apcu_fetch('Hello')); // 'World'

apcu_cache_info provides information about the store and its entries: print_r(apcu_cache_info()); Note that invoking apcu_cache_info() without limit will return the complete data currently stored. To only get the meta data, use apcu_cache_info(true). To get information about certain cache ...

The APCUIterator allows to iterate over entries in the cache: foreach (new APCUIterator() as $entry) { print_r($entry); } The iterator can be initialized with an optional regular expression to select only entries with matching keys: foreach (new APCUIterator($regex) as $entry) { pr...

When creating a std::unique_lock, there are three different locking strategies to choose from: std::try_to_lock, std::defer_lock and std::adopt_lock std::try_to_lock allows for trying a lock without blocking: { std::atomic_int temp {0}; std::mutex _mutex; std::thread t( [&...

/** * Set a custom add to cart URL to redirect to * @return string */ function custom_add_to_cart_redirect() { return 'http://www.yourdomain.com/your-page/'; } add_filter( 'woocommerce_add_to_cart_redirect', 'custom_add_to_cart_redirect' );

Recursive mutex allows the same thread to recursively lock a resource - up to an unspecified limit. There are very few real-word justifications for this. Certain complex implementations might need to call an overloaded copy of a function without releasing the lock. std::atomic_int temp{0}; ...

Compress-Archive -Path C:\Documents\* -CompressionLevel Optimal -DestinationPath C:\Archives\Documents.zip This command: Compresses all files in C:\Documents Uses Optimal compression Save the resulting archive in C:\Archives\Documents.zip -DestinationPath will add .zipif not present. -Li...

Compress-Archive -Path C:\Documents\* -Update -DestinationPath C:\Archives\Documents.zip this will add or replace all files Documents.zip with the new ones from C:\Documents

Expand-Archive -Path C:\Archives\Documents.zip -DestinationPath C:\Documents this will extract all files from Documents.zip into the folder C:\Documents

index.js var http = require("http"); http.createServer(function(request, response) { response.writeHead(200, {"Content-Type": "text/plain"}); response.write("Heroku world!"); response.end(); }).listen(process.env.PORT); package.json { &quo...

if (Patterns.EMAIL_ADDRESS.matcher(email).matches()){ Log.i("EmailCheck","It is valid"); }

The List interface is implemented by different classes. Each of them has its own way for implementing it with different strategies and providing different pros and cons. Classes implementing List These are all of the public classes in Java SE 8 that implement the java.util.List interface: Abs...

Vertical join appends dataset B to dataset A providing both of them have similar variables. For example, we have sales for the month of Jan'17 in dataset A and sales for Feb'17 in dataset B. To create a dataset C that has sales of both Jan and Feb we use Vertical Join. PROC SQL; CREATE TABLE C AS ...

Inner join creates a dataset that contains records that have matching values from both the tables. For example, we have a dataset A that contains customer information and a dataset B that contains credit card details. To get the credit card details of customers in dataset A, let us create dataset C ...

Like left join, right join selects all the observations from the right dataset and the matched records from the left table. PROC SQL; CREATE TABLE C AS SELECT A.*, B.CC_NUMBER, B.START_DATE FROM CUSTOMER A RIGHT JOIN CC_DETAILS B ON A.CUSTOMERID=B.CUSTOMERID QUIT; Dataset C contains all the...