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  Regular expression to get html meta description

When we need to process a HTML page source code, we often need to retrieve the meta description of the page besides the links in the page. This description is usually located in <meta> tag of a HTML page. The meta description is very useful for search engine index. How can we retrieve the meta description? If we use a regular expression, we can easily get the meta description. In JavaScript, the regular expression looks like : var pattern = /<meta.*?name="description".*?content="(.*?)"....

   Regular expression,meta description,HTML,JavaScript     2012-07-03 10:09:20

  How to Understand and Use nil in Golang Correctly?

In Golang, nil is a predefined identifier that carries different meanings in various contexts, but typically represents "none", "empty" or "zero value". It can be assigned to variables of pointer, slice, map, channel, function, and interface types. Understanding the significance of nil is crucial for writing robust Go programs, as mishandling nil can lead to unexpected issues. nil in Pointers In Go, pointers are a fundamental type that stores the memory address of a variable. When a pointer is d...

   FUNCTION,SLICE,MAP,CHANNEL,GOLANG,NIL     2024-01-05 05:19:40

  gethostbyname vs getaddrinfo

getaddrinfo is slower than ping when resolving domain names. I think ping uses gethostbyname to resolve a domain name. The question becomes whether getaddrinfo is slower than gethostbyname. After testing with both functions, we find that getaddrinfo is really slow compared to gethostbyname. By strace tracking,  we find getaddrinfo will communicate with DNS server 10 times and gethostbyname will communicate with DNS server communication twice.gethostbyname is an old way to resolve domain nam...

   C++,network,DNS     2012-08-15 14:06:34

  errGroup in GoLang explained

Today, let's talk about the usage and applicable scenarios of errGroup, which is often used. Why is it useful? Generally, when we use goroutine, we cannot return a value. If you want to pass out the result of the goroutine execution, you usually have to use the channel. The errGroup package is suitable if you want to know when the goroutine you opened encounters an error during execution and stop working, and I need to know the error value. errGroup usage The package needs to be downloaded and i...

   GOLANG,ERRGROUP,WAITHROUP,CONCURRENCY     2023-05-27 23:58:20

  Can two new objects point to the same memory address in GoLang?

Do you have any idea what the output will be for below GoLang snippet? package main import ( "fmt" ) type obj struct{} func main() { a := &obj{} fmt.Printf("%p\n", a) c := &obj{} fmt.Printf("%p\n", c) fmt.Println(a == c) } Many people would think that a and c are two different object instances which have different memory addresses. Hence a == c will be false. But if you try to run the above program, you would see below output 0x5781c8 0x5781c8 true To get to know the reason wh...

   GO,GOLANG,VARIABLE ESCAPE,ZEROBASE     2019-04-06 01:19:52

  Ensuring Go Interface Implementation: A Quick Guide

Introduction Go's simplicity and power shine in its interface system, offering a clean way to define contracts between types. However, when it comes to checking whether a struct satisfies an interface, Go's static typing philosophy means there isn't a direct runtime check. In this concise guide, we'll explore practical methods, including some lesser-known tricks, to verify whether a struct implements an interface. Method 1: Type Assertion and a Dummy Method package main import "fmt" type MyInt...

   INTERFACE,GOLANG,IMPLEMENTS     2023-11-25 21:36:01

  Set Theory in C++11

Have you ever felt the need to perform set theoretic operations on types? Not really? Me neither, but I thought it’s a fun thing to try out. So, if you ever feel the need of using type sets, C++11 makes it quite easy to do so. Especially variadic templates allow for a much more condensed syntax compared to type list constructs formerly used. (Disclaimer: This is rather a proof of concept, but maybe somebody comes up with a useful scenario.) Let’s start by d...

   C++,set theory,Math     2012-03-11 13:15:55

  Binary tree iterator algorithm

Binary tree pre-order,in-order and post-order traversal are basics in algorithm and data structure.And the recursive binary tree traversal is a classical application of recursion. We define a binary tree node as : // C++ struct Node { int value; Node *left; Node *right; } In order binary tree traversal can be: // C++ void inorder_traverse(Node *node) { if (NULL != node->left) { inorder_traverse(node->left); } do_something(node); if (NULL != node->righ...

   Binary tree,Iterator,Traversal     2013-07-14 21:51:09

  Function Pointers in C are Underrated

The function pointer in C is, in my opinion, one of the most ignored gems of the language. It’s the kind of feature you rarely need, and then suddenly, one day, you find yourself in dire need of it, as evidenced by the real-life use-case below. If you don’t know what a function pointer is in the first place, here’s the meat of it: it gives you the ability to pass a function around like a normal variable. If you know Python / Ruby / Lisp, you might know it by the name...

   C,Pointer,Analysis     2012-03-24 05:23:09

  Preprocessor magic:Default Arguments in C

This post is for programmers who like C or for one reason or another can't use anything else but C in one of their projects. The advantages of having default arguments is not something that needs convincing. It's just very nice and convenient to have them. C++ offers the ability to define them but C under the C99 standard has no way to allow it. In this post I will detail two ways I know of implementing default arguments in C. If a reader happens to know additional ways please share in ...

   C,Preprocessor,Default arguments     2012-02-19 06:17:04

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