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  Understanding JavaScript closure and where it can be used

Closure The official definition of closure is: an expression (usually a function) that has many variables and is bound to an environment that includes those variables. In JavaScript, closure refers to the ability of a function to access the lexical scope in which it was defined, even after the function has been executed and left that scope. This ability is due to the fact that when a function is created, it generates a closure that includes a reference to the definition environment of the curr...

   CLOSURE,JAVASCRIPT,USAGE     2023-03-05 02:17:08

  A Perl Regular Expression That Matches Prime Numbers

perl -lne '(1x$_) =~ /^1?$|^(11+?)\1+$/ || print "$_ is prime"' Can you figure out how it works? I give an explanation below, but try to figure it out yourself. Here is what happens when you run it: $ perl -lne '(1x$_) =~ /^1?$|^(11+?)\1+$/ || print "$_ is prime"' 1 2 2 is prime 3 3 is prime 4 5 5 is prime 6 7 7 is prime 8 9 10 11 11 is prime Here is how it works. First, the number is converted in its unary representation by (1x$_). For example, the number 5 gets converted into 1x5, which is ...

   Perl,Regex,Regular expression,Prime number,One line     2011-12-26 08:42:00

  To our youth

Youth is the best period in our life for most of us. We have dreams, passions and energies. We can work day and night for our dreams.We can hang out with friends the whole day. But there will always be a day when we are not young anymore, our youth will pass by. We will not be able to go back to our youth any more. Do you have anything to say about your youth? Recently, a Chinese IT engineer @本座 wrote a short code snippet to describe our youth. Here we share what she writes: public vo...

   Youth,Programming,Rollback     2013-05-02 05:26:56

  What will the value of Integer.valueOf(127) == Integer.valueOf(127) be in Java?

Do you really understand how Java does the integer comparison? OK, ignore the statements in the post title. What we are interested in is another set of comparison statements. Let's first see below code snippet. public class IntegerComparison { public static void main(String[] args) { Integer a = 127, b = 127; Integer c = 128, d = 128; System.out.println(a == b); System.out.println(c == d); } } What do you think the output will be? Are they both displaying true? You will find out t...

   JAVA,==,EQUALSTO     2018-01-13 22:18:15

  When and Where to Use Pointers in Go

When declaring variables in Go, we usually have two syntax options: In some scenarios, pointers; in others, reference; sometimes, either. It’s great to have choices, but it is also confusing sometimes as to which one in which scenario. To be more reasonable in choice-making, I started from pointers, walked through their natures, and summarized some rules in using them in Go. from unsplash, Jordan Ladikos Pointers Go has pointers. A pointer holds the memory address of a ...

   POINTER,GOLANG     2022-05-01 02:24:43

  A mini post on GoLang context

In a GoLang web server, every request coming in will be handled by a goroutine. In the request handler, the logic may also need to create new goroutine to handle other tasks like RPC call. When the request is processed and response is returned, these goroutines created need to be exited so that no goroutine leak should happen. package main import ( "fmt" "log" "net/http" ) func main() { http.HandleFunc("/echo", func(w http.ResponseWriter, r *http.Request) { fmt.Println(&r) w.Write(...

   CONTEXT,GOLANG     2019-12-14 06:21:02

  passing parameters to XMLHttpRequest’s onreadystatechange function

I’ve been smashing my head against this all day – but I finally got something working consistently and reliable, so I better damn well document it. This is as good a place as any, and hopefully it will be useful to others.I needed to make an Ajax call, so I turned to my good friend XMLHttpRequest. One wrinkle was that I needed to pass in a parameter to it… so I tried:var test = "bar"; req = new XMLHttpRequest(); req.open("GET", myURL, true); req.foo = test; req.onreadystatech...

   JavaScript,AJAX,XMLHttpRequest,parameter,onreadystatechange     2011-10-09 01:32:09

  Android create button tutorial

This tutorial assumes that you already have an activity and are using an XML layout. Open the layout XML and add the button element.  Assign an ID with the “@+id” operator.  The + tells Android to generate an ID for this element so that you can reference it in your Java files. This is an example. Your layout and text elements will probably be very different. In this example case, the ID of the button is “close”. <Button android:id="@+id/close" android:lay...

   Android,Simulator,Button,XML,Tutorial     2014-11-07 08:30:10

  Custom C++ exception class creation

In standard C++, we can use try catch to catch and exception when something goes wrong. These are some built in exception support in C++. By including the #include , we can now catch exceptions in C++ programs. This actually helps us on debugging our code and reduce the maintenance work.However sometimes if we want to create our own custom exception class. What should we do?We should include the #include line and then extend the exception class and implement some methods as you like. The genera...

   C++,std,exception,custom exception,implementation     2012-03-04 09:58:18

  C Preprocessor Hell

Lisp programmers should stop reading right now because they'll likely suffer severe injury of the jaw muscles as they laugh themselves silly at how hard it is to do some things in C. The C language has a pre-processor (typically called cpp) that is both infuriating and powerful. How powerful is usually best described as 'just too little' and it has happened more than once that I found myself almost - but not quite - able to do what I wanted to do. The frustration can run very deep at ti...

   C,Preprocessor,Lisp,Hell     2012-01-19 10:22:31

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