基本 C++ 程式碼整理 (Basic C++ Notes)

Revised: 2023/4/11

基本 C++ 程式碼整理如下

Reference: I Horton, Ivor Horton's Beginning Visual C++ 2013 (Wiley 2014).


Main Function
. #include <cstring>     // For strlen() ans strcpy()
. #include <iostream>  // Basic input and output library
. #include <utility>      // Define a set of templates for operator functions; For operator overload templates
. using namespace std::rel_ops;  // The templates are defined in the std::rel_ops namespace
. #include "CandyBox.h"            // For class CBox and class CCandyBox
. using namespace std;                // Any name in std namespace


Header File
. #pragma once  // Prevent the file contents from being included in the source code more than once 

. #include "Box.h"                           // In inherited class CCandyBox 

. #include "CandyBox.h"                // For CBox and CCandyBox

. class CCandyBox : public CBox  // In inherited class CCandyBox; private CBox or CBox

. explicit CBox(double side) : m_Length {side}, m_Width {side}, m_Height {side} {}  // Specific constructor

. #include <fstream>

      ofstream myfile;  // Write

      myfile.open ("example.txt");

      myfile << "Writing this to a file.\n";

      myfile.close()

. #include <fstream> 

  #include <string>

  string line;

  ifstream myfile("example.txt");  // Read

  while (getline(myfile, line))

  {

  cout << line << '\n';

  }

  myfile.close();

#include <iostream>

  int number;  // Or int number = int();

  cout << "Enter a number: ";

  cin >> number;

  cout << "The number is: " << number << endl;

#include <fstream>  // Output with file (file stream 的縮寫)

ofstream myfile;

ofstream myfile1;

myfile.open("data.txt");

myfile1.open("rate.txt");

myfile << x << endl;

myfile1 << y << endl;

Basic Commands
. log(x)           // Natural logarithm of x

. log10(x)       // Logarithm of x

. exp(5.0)       // = 148.413159

. abs(-1.0)      // = 1

  fabs(-1.0)     // = 1

. acos(-1.0)    // = pi

. sqrt(143.0)  // = 11.9583

. pow(5.0, 3)  // = 125

. \                  // Backslash as a line continuation character
      a = 1.0 + 2.0;
      or
      a = 1.0 + \
            2.0;

. logical operators: &&, ||, !

. system("pause")  // Pause

. if
       for ()

       {

           if ()

          {

              statement 1;

              statement 2;

          }

       }

      if (i > 7) x = 6;


      if (j % 2 == 0)  // j is even
          K2 = K2 + Q;
      else                  // j is odd
          K3 = K3 + Q;


      if (i == 0 || i == n)
          J1 = J1 + L; 
      else if (i % 2 == 0)
          J2 = J2 + L;
      else           
          J3 = J3 + L;

. for
      for (int i{0}; i <= n - 1; i++)  // or int i{}

. switch
      switch(dice)
      {
          case 1: cout << pstr << pstr1;
                      a = 1.0;
                      break;
          case 2: cout << pstr << pstr2;
                      break;
          case 3: cout << pstr << pstr3;
                      break;
          case 4: cout << pstr << pstr4;
                      break;
          case 5: cout << pstr << pstr5;
                      break;
          case 6: cout << pstr << pstr6;
                      break;       
          default: cout << "Sorry, you haven't got a lucky star.";

      }

. return
  (1) ok
        if (FP == 0.0 || ((b - a) / 2.0) < tol)
           return p;  // Output p; procedure completed successfully
  (2) ok
        if (FP == 0.0 || ((b - a) / 2.0) < tol)
        {
           return p;  // Output p; procedure completed successfully
        }  
  (3) ok
        if (FP == 0.0 || ((b - a) / 2.0) < tol)
       {
            cout << "Root: " << p << endl;
           return p;  // Output p; procedure completed successfully
       }
 (4) failed
       if (FP == 0.0 || ((b - a) / 2.0) < tol)
      {}
      return p;  // Output p; procedure completed successfully
 (5) failed
       if (FP == 0.0 || ((b - a) / 2.0) < tol)
           cout << "Root: " << p << endl;
          return p;  // Output p; procedure completed successfully

. to comment-out (multi-line comments)
   /*
   cout << "The message is disabled" << endl;
  */

. 變動的檔名

#include <iostream>

#include <fstream> // Output with file

#include <string>

using namespace std;

int main()

{

std::string HistoryFilename = "temperature (n=" + std::to_string(0.5) + ")";

ofstream myfile;

myfile.open(HistoryFilename + ".txt");

myfile << 123 << endl;

myfile.close();

return 0;

}