Demo program for Week 3, CS31 Fall 2021 Discussion 1C

week3.cpp

/* Demo program for CS31 Discussion 1C Week 3
   Oct 15, 2021, Mingyu Derek Ma
*/
#include <iostream>
#include <string>
#include <cctype>
using namespace std;

void example1(){
    // Print out positive integer 1~n inclusively
    int n = -1;
    
    // For loop
    // Style 1
    for (int i = 1; i <= n; ++i){
        cout << i << endl;
    }
    // Style 2
    cout << "----" << endl;
    int i = 1;
    for (; i <= n ; ++i){
        cout << i << endl;
    }
    // Style 3
    cout << "----" << endl;
    i = 1;
    for (; i <= n ;){
        cout << i << endl;
        ++i;
    }
    // Style 4
    cout << "----" << endl;
    i = 1;
    for (;;){
        if (i > n)
            break;
        cout << i << endl;
        ++i;
    }
    
    // While loop
    cout << "---- while loop" << endl;
    i = 1;
    while (i <= n){
        cout << i << endl;
        ++i;
    }
    
    // do...while loop
    cout << "---- do while loop" << endl;
    i = 1;
    do {
        cout << i << endl;
        ++i;
    } while (i <= n);
    
    // Test input: 5 -1
}

void example2(){
    char input;
    cout << "Enter any character: ";
    cin >> input;
    cout << "The character you entered is: " << input << endl;
    cout << "Its ASCII code is: " << int(input) << endl;
    
    // Arithmetic and relational operations
    cout << "---" << endl;
    cout << '\n' << endl;
    if ('a' < 'b'){
        cout << "In true branch because char a is smaller than char b" << endl;
    }
    cout << 'a' - 32 << endl;
    cout << char('a' - 32) << endl;
    cout << 'x' + ('A' - 'a') << endl;
    cout << char('x' + ('A' - 'a')) << endl;
    
    // Some function enabled by include <cctype>
    cout << "---" << endl;
    if (isalpha(input))
        cout << "That's an alphabetic character.\n";
    if (isdigit(input))
        cout << "That's a numeric digit.\n";
    if (islower(input))
        cout << "The letter you entered is lowercase.\n";
    if (isupper(input))
        cout << "The letter you entered is uppercase.\n";
    if (isspace(input))
        cout << "That's a whitespace character.\n";
    cout << tolower(input) << endl;
    cout << char(tolower(input)) << endl;
    cout << toupper(input) << endl;
    cout << char(toupper(input)) << endl;
}

void example3(){
    cout << "Enter a string: ";
    string s = "abcdefghijklmnopq";
    getline(cin, s);
    cout << "String size: " << s.size() << endl;
    for (int i=0; i<s.size(); i++){
        cout << i << " " << s[i] << s.at(i) << endl;
        if (s.at(i)=='h') { // note we are using char H rather than string H for condition
            if (s.at(i+1)=='e')
                cout << "We found a mention of \"he\" at index " << i << endl;
        }
    }
    // Testing examples
    // He likes to tell joke, he just told one.
    //     it will work for this input
    // abcdefghijklmn
    //     it will work for this input
    // abcdefgh
    //     undefined behavior since i+1 for s.at(i+1) is \0
}

int main(){
    example1();
//    example2();
//    example3();
}