Author: fighternan

Summary In this post, I will introduce const, * and & and their combinations. I also have similar posts discussed auto and &. Conclusion As usual, I present the golden rule first: “read from right to left”. In other words, the const-on-the-right style always puts the const on the right of what it constifies”. When…

Summary In this post, I will discuss when to use References and when to use Pointers in C++. Conclusion As usual, I present the conclusion first. 1. If the varible can be nullptr, declare the varible as a pointer; 2. If the you want to re-assign the varible, declare the varible as a pointer; 3….

Summary I come across a compiling error, in which it says class A was not declared. However, I actually include A.h. Details After some research, I find out the bugs. In utils.h, I want to use some static member varible in class A and thus I include A.h. However, since utils.h acts as its name,…

Summary In this post, we will discuss rvalue references and move semantics in C++11. Details Rvalue references and move semantics can be very complex, see this article. But the truth is that: the simplest is the best. It starts with three examples of returning values from functions. Read them and ask yourself which of them…

Summary In this post, I will introduce how to get a vector of files in a directory in C++. Instead of filesystem in boost or C++ 17, this method is purely based on C++ 11 and Unix platforms. Details The following codes are self-explained. // safe path join in unix-based system string path_join(const string& p1,…

Summary It is another post related to String in C++. I will introduce some useful codes which implement APIs in Java String. Content String.startsWith() String.endsWith() String.toLowerCase() String.toUpperCase() String.trim() Detials 1. String.startsWith() We implement a.startsWith(b) of java using C++. bool starts_with(const string & a, const string & b) { return b == a.substr(0, b.size()); } int…

Summary In this post, I will introduce lvalues and rvalues in C/C++. But I leave rvalue references and move semantics to the next post. Details Definition Lvalues: (locator value) represents an object that occupies some unique location in memory (has an address in some scope). Rvalues: not lvalues. Important points and examples 1. Rvalues can’t…

Summary In this post, I will show delegating constructors introduced in C++ 11. Details I come across the codes below, and get confused about the systax. class Iterator { struct Data; Data* data; public: Iterator(const vector<int>& nums); Iterator(const Iterator& iter); virtual ~Iterator(); int next(); bool hasNext() const; }; class PeekingIterator : public Iterator { private:…

Summary In this post we will discuss how to change object while iterating it. Details Say we have a map. unordered_map<char, int> char_counter ({{‘1’, 1}, {‘a’, 1}, {‘b’, 2}, {‘c’, 3}}); Now, we want to delete all elements whose value is 1. To delete an element using iterator we will use erase() function. But the…

Summary In this post, I will introduce some syntax sugar in C++. Content 1. Initializer List Constructor 2. Range in Container Construtor 3. Copy Constructor Details 1. Initializer List Constructor vector<int> vec({1,2,3,4,5}); unordered_map<char, int> char_counter ({{‘a’, 1}, {‘b’, 2}, {‘c’, 3}}); The syntax below is also legal. // use {} in vector vector<int> nums =…

Summary In this post, I will introduce the string class in c++ STL. It covers useful APIs and some of my recommendations. 1. Split 2. Access 3. Comparison 4. Numeric-Conversions Details Split Thanks to this post, we present the conlusions for split first. 1. If you have access to boost, please do Solution 1. 2….

Summary In this post, I will introduce auto, const auto, auto&, const auto&, auto&&, and const auto&&. Conclusion We provide the conclusion first. When you want a read-only access (generic or non-generic codes), use auto const &, which will give you a reference rather than a copy. When you want a read-write access in generic…

Summary This post will be updated from time to time. The post contains some mistakes that I will make in work and study when coding in C++. Contents container.size() – 1 when the container is empty negative % positive ‘+’ does work in “C_String” remember to delete after new to_string(‘a’) signed integers compared to unsinged…

Summary In this post, I will introduce auto and decltype in C++ 11. Why Auto In some situations, auto makes codes more readable. It will tell the compiler to deduce the type of a declared variable from the initialization expression. The details are complex. At present, we want to make codes correct, clean, and simple….

Summary In this post, I will introduce the map and priority_queue in c++ STL. Why Ordered Containers Unlike the easy version unordered_map, in map, key values are generally used to sort. Thanks to the binary search tree, map has good performance in search and erase elements $(log(n))$. Constructor The following codes are self-explained. // Example…