Control Statement_1-程式設計筆記

Chapter 3, Control Statement_1

Control Structure

• The sequence structure
• The selection strcture
• The repetition structure

Selection Statements

• To choose among courses of action.
• if: A single-selection statement
• if...else: A double-selection statement
• switch: A multiselection statement

Conditional Operators(?:)

• Closely related to the if..else function.

Ex:

#include <iostream>
int main(){
    int x{0}, y{1};
    result=x<y?"x<y":"x>y";
    std::cout<<result;
}

Accodring to the code, it will cout xy in the command prompt.

• Another way to declare integers: int x{0} equals to int x=0

Repetition Statements(Looping Statements)

• while: do the action zero or more times.
• do...while: do the action at least once.
• for: do the action zero or more times.

Counter Controlled Repetition

• Counter variables are normally initialized to zero or one, depending on their use.
• Remember to initialize the counter varible, or it might contain some garbage variable.

How to change the tpye of a object

#include <iostream>
int main(){
    static_cast<type>(object);
    (type)object;
}

setprecision()

#inlcude <iostream>
#include <iomanip>
int main(){
    std::cout<<std::setprecision(2)<<floatnum; //start from the first num after fixed point
    std::cout<<fixed::std::setprecision(2)<<floatnum; //start from the first num before fixed point
}

Common Keywords in C++ and C

Assignment Operators

Preincrement and Postincrement

• Preincrement => Increment a by 1, then use the new value of a in the expression in which a resides.
• Postincrement => Use the current value of a in the expression in which a resides, then increment a by 1.

Ex:

#include <iostream>
using namespace std;
int main(){
    int a=1;
    cout<<a<<"\n";
    cout<<a++<<"\n";
    //do a=a+1 after cout
    int b=1;
    cout<<b<<"\n";
    cout<<++b<<"\n";
    //do b=b+1 before cout
}