a45s67 / CPlusPlus-Cheatsheet

CPlusPlus-Cheatsheet

Tricks

• Generate string repetition of given length. so

// repeat one char
std::string s(5, 'a'); // s == "aaaaa"

// repeat string
#include <algorithm>

std::string pattern("Xeo ");
auto pattern_it = pattern.begin();
std::string s(256, '\0');
std::generate(s.begin(), s.end(),
    [&]() -> char { 
      if(pattern_it == pattern.end())
        pattern_it = pattern.begin();
      return *pattern_it++; // return current value and increment
    });

Class

• Initializations

struct B
{
    explicit B(int) { }
    explicit B(int, int) { }
    explicit operator bool() const { return true; }
};
 
int main()
{

//  B b1 = 1;      // error: copy-initialization does not consider B::B(int)
    B b2(2);       // OK: direct-initialization selects B::B(int)
    B b3 {4, 5};   // OK: direct-list-initialization selects B::B(int, int)
//  B b4 = {4, 5}; // error: copy-list-initialization does not consider B::B(int,int)
    B b5 = (B)1;   // OK: explicit cast performs static_cast
    if (b2) ;      // OK: B::operator bool()
//  bool nb1 = b2; // error: copy-initialization does not consider B::operator bool()
    bool nb2 = static_cast<bool>(b2); // OK: static_cast performs direct-initialization
}
// reference : https://en.cppreference.com/w/cpp/language/explicit

• Operator overloading
  1. Design of Operator +

// 先設計 += 再設計 +
Point const operator+(Point const &lhs, Point const &rhs) // 
{
  return Point(lhs) += rhs; // 
}

// [心得] operator+ 與 operator+= 的設計
// https://www.ptt.cc/man/C_and_CPP/D8D2/DA94/DDBB/M.1127480887.A.E7F.html

• Rvalue

  • [C++] rvalue reference 初入門
    • lvalue, rvalue, &&, use of std::move
  • What is move semantics?

• RAII

Syntax

• 潮．C++20 | explicit 關鍵字大解析
• All declarations
  • asm, inline, &, constexpr, ...

// A sample in the article, wtf
int (*(*foo)(double))[3] = nullptr;

Compiler behaviour

• Optimize
  • 什么时候应当依靠返回值优化（RVO）
• Resource allocation
  • RAII

Reading list

• Effective Modern C++
• Clean Code: A Handbook of Agile Software Craftsmanship
• [Almost Done]
  • 程序員的自我修養:鍵結,裝載與庫