Tutorial by Examples: for

Variable substitutions should only be used inside double quotes. calculation='2 * 3' echo "$calculation" # prints 2 * 3 echo $calculation # prints 2, the list of files in the current directory, and 3 echo "$(($calculation))" # prints 6 Outside of doubl...

Go programs end when the main function ends, therefore it is common practice to wait for all goroutines to finish. A common solution for this is to use a sync.WaitGroup object. package main import ( "fmt" "sync" ) var wg sync.WaitGroup // 1 func routine(i int...

To instantiate Foldable you need to provide a definition for at least foldMap or foldr. data Tree a = Leaf | Node (Tree a) a (Tree a) instance Foldable Tree where foldMap f Leaf = mempty foldMap f (Node l x r) = foldMap f l `mappend` f x `mappend` foldMap f r fo...

import Data.Traversable as Traversable data MyType a = -- ... instance Traversable MyType where traverse = -- ... Every Traversable structure can be made a Foldable Functor using the fmapDefault and foldMapDefault functions found in Data.Traversable. instance Functor MyType where ...

Implementations of traverse usually look like an implementation of fmap lifted into an Applicative context. data Tree a = Leaf | Node (Tree a) a (Tree a) instance Traversable Tree where traverse f Leaf = pure Leaf traverse f (Node l x r) = Node <$> traverse f l <*...

Sometimes you may have a form and want to submit it using ajax. Suppose you have this simple form - <form id="ajax_form" action="form_action.php"> <label for="name">Name :</label> <input name="name" id="name" type="t...

Array types inherit their equals() (and hashCode()) implementations from java.lang.Object, so equals() will only return true when comparing against the exact same array object. To compare arrays for equality based on their values, use java.util.Arrays.equals, which is overloaded for all array types...

You can use a colon and the standard numeric format syntax to control how numbers are formatted. var decimalValue = 120.5; var asCurrency = $"It costs {decimalValue:C}"; // String value is "It costs $120.50" (depending on your local currency settings) var withThreeDecimal...

The following syntax indicate that a class adopts a protocol, using angle brackets. @interface NewClass : NSObject <NewProtocol> ... @end This means that any instance of NewClass will respond to methods declared in its interface but also it will provide an implementation for all the requ...

Closures are often used for asynchronous tasks, for example when fetching data from a website. 3.0 func getData(urlString: String, callback: (result: NSData?) -> Void) { // Turn the URL string into an NSURLRequest. guard let url = NSURL(string: urlString) else { return } let re...

Chef Scollector Cookbook: https://github.com/alexmbird/chef-scollector Chef Bosun Cookbook: https://github.com/ptqa/chef-bosun Puppet scollector module: https://github.com/axibase/axibase-puppet-modules Bosun Ansible/Vagrant example: https://github.com/gnosek/bosun-deploy

docker ps --format 'table {{.ID}}\t{{.Names}}\t{{.Status}}'

public class CustomFormat : IFormatProvider, ICustomFormatter { public string Format(string format, object arg, IFormatProvider formatProvider) { if (!this.Equals(formatProvider)) { return null; } if (format == "Reverse") ...

// Create a block with an asynchronous action var block = new ActionBlock<string>(async hostName => { IPAddress[] ipAddresses = await Dns.GetHostAddressesAsync(hostName); Console.WriteLine(ipAddresses[0]); }); block.Post("google.com"); // Post items to the block's ...

If you have several objects of monadic types, we can achieve combinations of the values using a 'for comprehension': for { x <- Option(1) y <- Option("b") z <- List(3, 4) } { // Now we can use the x, y, z variables println(x, y, z) x // the last expre...

CREATE TABLE Account ( AccountID INT UNSIGNED NOT NULL, AccountNo INT UNSIGNED NOT NULL, PersonID INT UNSIGNED, PRIMARY KEY (AccountID), FOREIGN KEY (PersonID) REFERENCES Person (PersonID) ) ENGINE=InnoDB; Foreign key: A Foreign Key (FK) is either a single col...

The FOR XML PATH can be used for concatenating values into string. The example below concatenates values into a CSV string: DECLARE @DataSource TABLE ( [rowID] TINYINT ,[FirstName] NVARCHAR(32) ); INSERT INTO @DataSource ([rowID], [FirstName]) VALUES (1, 'Alex') ,(2, 'Peter') ...

Installing package manager Homebrew brew Paste that at a Terminal prompt. /usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)" Installing Xcode IDE Download it using link below or find it on Mac App Store https://developer.apple.com/down...

Normally you would want to avoid using cursors as they can have negative impacts on performance. However in some special cases you may need to loop through your data record by record and perform some action. DECLARE @orderId AS INT -- here we are creating our cursor, as a local cursor and only a...

Assuming python and python3 are both installed, it is possible to create a virtual environment for Python 3 even if python3 is not the default Python: virtualenv -p python3 foo or virtualenv --python=python3 foo or python3 -m venv foo or pyvenv foo Actually you can create virtual ...