Tutorial by Examples: at

Create an input port

An input port can be created in many ways, but usually the method starts with open-input-. String port You can use a string as a port using open-input-string. It will create a port that will be able to read from the string. (define p (open-input-string "(a . (b . (c . ()))) 34")) ...

Create a pair

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...

Create a list with pairs

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...

typedef enum declaration in Objective-C

A enum declares a set of ordered values - the typedef just adds a handy name to this. The 1st element is 0 etc. typedef enum { Monday=1, Tuesday, Wednesday } WORKDAYS; WORKDAYS today = Monday;//value 1

Installation or Setup

Detailed instructions on getting automation set up or installed.

Confirming Navigation request using OnNavigatingFrom

private bool navigateFlag = false; protected async override void OnNavigatingFrom(NavigatingCancelEventArgs e) { base.OnNavigatingFrom(e); if (!navigateFlag) { e.Cancel = true; var dialog = new MessageDialog("Navigate away?", Confir,); ...

unique and duplicated no longer works on keyed data.table

This is for those moving to data.table >= 1.9.8 You have a data set of pet owners and names, but you suspect some repeated data has been captured. library(data.table) DT <- data.table(pet = c("dog","dog","cat","dog"), owner = c(&quot...

Alternative definition

Since every Applicative Functor is a Functor, fmap can always be used on it; thus the essence of Applicative is the pairing of carried contents, as well as the ability to create it: class Functor f => PairingFunctor f where funit :: f () -- create a context, carrying nothing ...

How you create a tri-color attributed string.

NSMutableAttributedString * string = [[NSMutableAttributedString alloc] initWithString:@"firstsecondthird"]; [string addAttribute:NSForegroundColorAttributeName value:[UIColor redColor] range:NSMakeRange(0,5)]; [string addAttribute:NSForegroundColorAttributeName value:[UIColor greenColo...

Installation or Setup

Firebase Cloud Messaging is the Firebase service that handles push notifications. You can add this service in any client: web, Android or IOS. The specific functioning for each must be read from the documentation. For adding FCM in any type of project, is always adding a library. Considering the s...

Sending multi-dimensional data and multiple files with CurlFile in one request

Let's say we have a form like the one below. We want to send the data to our webserver via AJAX and from there to a script running on an external server. So we have normal inputs, a multi-select field and a file dropzone where we can upload multiple files. Assuming the AJAX POST request was succ...

Create a view with schema binding

If a view is created WITH SCHEMABINDING, the underlying table(s) can't be dropped or modified in such a way that they would break the view. For example, a table column referenced in a view can't be removed. CREATE VIEW dbo.PersonsView WITH SCHEMABINDING AS SELECT name, address FROM d...

Common instances of Applicative

Maybe Maybe is an applicative functor containing a possibly-absent value. instance Applicative Maybe where pure = Just Just f <*> Just x = Just $ f x _ <*> _ = Nothing pure lifts the given value into Maybe by applying Just to it. The (<*>) function applies...

JSP out implicit object - simply displaying date and time.

<html> <body> <% out.print("Today is:"+java.util.Calendar.getInstance().getTime()); %> </body> </html>

Intro to Data Structures

A data structure is a way of organizing and storing information. Let a "Hello, World!" string be the information that we need to organize and store in byte-addressable memory. Each ASCII character requires 7 bits of storage. Most systems reserve 8 bits (1 byte) for each character, so eac...

Decompile Database

This should always be your initial fix. A good policy is to decompile the database before each release. Create a decompile shortcut. This loads the database with a "/decompile" switch. Right Click your Database File. Select Copy Right Click in the explorer window and select &quot...

Remove Binary Data from Form

Sometimes the crashes occur constantly in a single form or report, or occur only when printing. It is possible that the binary data within the form / report has become corrupt. Save the Form / Report object as text There are two undocumented functions. Application.SaveAsText and Application.Load...

Rebuild the entire database

This is a lot of work, so do this as a last resort after exhausting all other options. You only need to do this if the problem is occurring for different users, on different machines. If it isn't occurring for all users, then most likely it is not a corrupt database container. Similar to the steps...

Installation of Pyglet

Install Python, go into the command line and type: Python 2: pip install pyglet Python 3: pip3 install pyglet

The C++ compilation process

When you develop a C++ program, the next step is to compile the program before running it. The compilation is the process which converts the program written in human readable language like C, C++ etc into a machine code, directly understood by the Central Processing Unit. For example, if you have a...

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