Tutorial by Examples: ai

SELECT 3 * NULL + 5, 'Hello ' || NULL || 'world' from DUAL; 3*NULL+5'HELLO'||NULL||'WORLD'(null)Hello world

There is a particular syntax that allow us to write cons cell in a more compact way than using the cons constructor. A pair can be written as such: '(1 . 2) == (cons 1 2) The big difference is that we can create pairs using quote. Otherwise, Scheme would create a proper list (1 . (2 . '())). T...

A pair can be create with the cons function. The name of the function stand for constructor. In Scheme, everything is pretty much based on pairs. (cons a b) The function return a pair containing the element a and b. The first parameter of cons is called car (Content Address Register) and the sec...

The data in the pair can be accessed with utility functions. To access the car, we have to use the car function. (car (cons a b)) > a Also we can verify the following equality: (eq? a (car (cons a b))) > #t

To access the cdr, we have to use the cdr function. (cdr (cons a b)) b Also we can verify the following equality: (eq? b (cdr (cons a b))) #t

List in scheme are nothing else than a series of pairs nested in each other in the cdr of a cons. And the last cdr of a proper list is the empty list '(). To create the list (1 2 3 4), we'd have something like this: (cons 4 '()) > (4) (cons 3 (cons 4 '())) > (3 4) (cons 2 (cons 3 (cons 4...

Introduction NMAKE is a command-line utility developed by Microsoft to be used primarily in conjunction with Microsoft Visual Studio and/or the Visual C++ command line tools. NMAKE is build system that falls under the Make family of build systems, but has certain distinct features that diverge fro...

The first to thing to have: a model that contains a has_many relation with another model. class Project < ApplicationRecord has_many :todos end class Todo < ApplicationRecord belongs_to :project end In ProjectsController: class ProjectsController < ApplicationController d...

Ifconfig List all the interfaces available on the machine $ ifconfig -a List the details of a specific interface Syntax: $ ifconfig <interface> Example: $ ifconfig eth0 eth0 Link encap:Ethernet HWaddr xx:xx:xx:xx:xx:xx inet addr:x.x.x.x Bcast:x.x.x.x Mask:x.x.x.x ...

File: /etc/resolv.conf contains a list of DNS servers for domain name resolution Sample contents of the file: nameserver 8.8.8.8 # IP address of the primary name server nameserver 8.8.4.4 # IP address of the secondary name server In case internal DNS server you can validate if this server reso...

IMPORTANT This is just an example code, do not use in production. In order to download an header chain we have to send a getHeaders message. In this example we will require as much as possible headers after the 40000th one.The peer will respond with batch of 2000 headers so, we have to take the la...

In object-oriented design, the chain-of-responsibility pattern is a design pattern consisting of a source of command objects and a series of processing objects. Each processing object contains logic that defines the types of command objects that it can handle; the rest are passed to the next proce...

Native implementations The <template> element is implemented in every modern browsers: Chrome, Edge, Firefox, Opera, Safari, ... Custom Elements customElements.define(), Shadow DOM attachShadow() and HTML Imports <link rel="import"> are implemented in the latest ver...

This works, but there are a couple of things we need to do for our plugin to survive in the real world. One of jQuery's features is chaining, when you link five or six actions onto one selector. This is accomplished by having all jQuery object methods return the original jQuery object again (there a...

You can delete trailing spaces with the following command. :%s/\s\+$//e This command is explained as follows: enter Command mode with : do this to the entire file with % (default would be for the current line) substitute action s / start of the search pattern \s whitespace character \+ e...

func isValidEmail(email: String) -> Bool { let emailRegEx = "[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,4}" let emailTest = NSPredicate(format:"SELF MATCHES %@", emailRegEx) return emailTest.evaluate(with: email) } or you could use String extensio...

When it comes to dealing with timing issue, it is tempting and easy to put a "quick" browser.sleep(<timeout_in_milliseconds>) and move on. The problem is, it would some day fail. There is no golden/generic rule on what sleep timeout to set and, hence, at some point due to network or...

In a saved search formula, the possible values of mainline are designed to be useful in an HTML context. When mainline is true, the value of {mainline} is the 1-character string * (asterisk). When mainline is false, the value of {mainline} is the 6-character string   (non-breaking space, HT...

If you haven't already lets simply start this file of with: class HelloWorldLeftAndMain extends LeftAndMain { } Configure The first thing you should do, is define the $url_segment that will be used to access the interface, and the title ($menu_title) that will appear in the side navigation m...

The expected structure of this template can be a bit convoluted but it all boils down to this: There are 3 sections worth noting for this guide: .north .center .south It must be wrapped entirely within an element that has the data-pjax-fragment="Content" attribute. This is...