Control Statement_2-程式設計筆記

Chapter 4, Control Statement_2

do...while

do{

}while;(condition)

• do...while always check the continuation after the code inside the {} has been excecuted. Therefore, it will execute at least one time.

switch case

switch(expression){
    case constant1:
        //execute while expression is constant1;
        break;
    case constant2:
        //execute while expression is constant2;
        break;
    case 'F':
    case 'f':
        //execute while expression is F or f;
        break;
    .
    .
    .
    case 3+2:
        //not allowed
    case 1+4:
        //not allowed
    
    default:
        ...
        //code to be executed if expression doesn't
        // match any constant
        
}

• Perform many different actions based on the value of expression.

setw()

• setw() => print spaces to make it tidy.

EOF

• EOF => End of file by entering ctrl+z.

  cin>>sth;
  while(cin.get()!=EOF){
      ...
  }

cin.get() vs cin>>

• cin.get() -> only read one character.
• cin -> depends on >>.

  #include <iostream>
  int main(){
      int grade, aC{0}, bC{0}, cC{0};
      while((grade=std::cin.get())!=EOF){
          switch(grade){
          case 'a':
              aC++;
              break;
          case 'b':
              bC++;
              break;
          case 'c':
              cC++;
              break;
          case '\n':
          case '\t':
          case ' ':
              break;
          }
      }
      std::cout<<aC<<' '<<bC<<' '<<cC;
  }

C++ Modified Data Types

Continue vs Break

• Continue -> Only skip a specific process.
• Break -> Skip the whole process.

Boolalpha

std::cout<<true<<"\n";
std::cout<<std::boolalpha;
std::cout<<true<<"\n";
//The result will be 1 and true.

Operator's Precedence

• The right side of the && will only be considered if the left side is true.
• The && operator has a higher precedence than ||.
• Any nonezero value is interpreted as ture. Which means if(a=5){...} will be true.