Tutorial by Examples: s

async.waterfall(tasks, afterTasksCallback) will execute a set of tasks. Each task are executed after another, and the result of a task is passed to the next task. As async.series(), if a task fails, async stop the execution and call immediately the main callback. When tasks are finished successfull...

Dropping the database is a simple one-liner statement. Drop database will delete the database, hence always ensure to have a backup of the database if required. Below is the command to drop Employees Database DROP DATABASE [dbo].[Employees]

SELECT name, caption as title, year, pages FROM books UNION SELECT name, title, year, 0 as pages FROM movies When combining 2 record sets with different columns then emulate the missing ones with default values.

extern int var; static int var; /* Undefined behaviour */ C11, §6.2.2, 7 says: If, within a translation unit, the same identifier appears with both internal and external linkage, the behavior is undefined. Note that if an prior declaration of an identifier is visible then it'll have the pri...

Use the yum command to manage packages in Enterprise Linux-based operating systems: yum install php This installs a minimal install of PHP including some common features. If you need additional modules, you will need to install them separately. Once again, you can use yum to search for these pac...

To start, gemfiles require at least one source, in the form of the URL for a RubyGems server. Generate a Gemfile with the default rubygems.org source by running bundle init. Use https so your connection to the server will be verified with SSL. source 'https://rubygems.org' Next, declare the gem...

You should always use <?php ?> tags or short-echo tags <?= ?>. Other variations (in particular, short tags <? ?>) should not be used as they are commonly disabled by system administrators. When a file is not expected to produce output (the entire file is PHP code) the closing ?&gt...

Customizing the Shell prompt Default command prompt can be changed to look different and short. In case the current directory is long default command prompt becomes too large. Using PS1 becomes useful in these cases. A short and customized command pretty and elegant. In the table below PS1 has be...

git log --graph --pretty=format:'%C(red)%h%Creset -%C(yellow)%d%Creset %s %C(green)(%cr) %C(yellow)<%an>%Creset' The format option allows you to specify your own log output format: ParameterDetails%C(color_name)option colors the output that comes after it%h or %Habbreviates commit hash (us...

The easiest option to draw a circle, is - obviously - the rectangle function. %// radius r = 2; %// center c = [3 3]; pos = [c-r 2*r 2*r]; rectangle('Position',pos,'Curvature',[1 1]) axis equal but the curvature of the rectangle has to be set to 1! The position vector defines the rect...

Firstly, one can use quiver, where one doesn't have to deal with unhandy normalized figure units by use of annotation drawArrow = @(x,y) quiver( x(1),y(1),x(2)-x(1),y(2)-y(1),0 ) x1 = [10 30]; y1 = [10 30]; drawArrow(x1,y1); hold on x2 = [25 15]; y2 = [15 25]; drawArrow(x2,y2) ...

Improper Inheritance Lets say there are 2 classes class Foo and Bar. Foo has two features Do1 and Do2. Bar needs to use Do1 from Foo, but it doesn't need Do2 or needs feature that is equivalent to Do2 but does something completely different. Bad way: make Do2() on Foo virtual then override it in B...

C# developers get a lot of null reference exceptions to deal with. F# developers don't because they have the Option type. An Option<> type (some prefer Maybe<> as a name) provides a Some and a None return type. It makes it explicit that a method may be about to return a null record. For...

One of Angular's strength's is client-side form validation. Dealing with traditional form inputs and having to use interrogative jQuery-style processing can be time-consuming and finicky. Angular allows you to produce professional interactive forms relatively easily. The ng-model directive provide...

uses System.Character; var S1, S2: string; begin S1 := 'Foo'; S2 := ToLower(S1); // Convert the string to lower-case S1 := ToUpper(S2); // Convert the string to upper-case

2009 uses Character; var C1, C2: Char; begin C1 := 'F'; C2 := ToLower(C1); // Convert the char to lower-case C1 := ToUpper(C2); // Convert the char to upper-case The uses clause should be System.Character if version is XE2 or above.

The assignment operator = sets thr left hand operand's value to the value of right hand operand, and return that value: int a = 3; // assigns value 3 to variable a int b = a = 5; // first assigns value 5 to variable a, then does the same for variable b Console.WriteLine(a = 3 + 4); // prints ...

To display "Some Text", use the command: echo Some Text This will output the string Some Text followed by a new line. To display the strings On and Off (case insensitive) or the empty string, use a ( instead of white-space: echo(ON echo( echo(off This will output: ON off ...

The echo setting determines whether command echoing is on or off. This is what a sample program looks like with command echoing on (default): C:\Windows\System32>echo Hello, World! Hello, World! C:\Windows\System32>where explorer C:\Windows\System32\explorer.exe C:\Windows\System32&gt...

enum Util { /* No instances */; public static int clamp(int min, int max, int i) { return Math.min(Math.max(i, min), max); } // other utility methods... } Just as enum can be used for singletons (1 instance classes), it can be used for utility classes (0 instance...