C++ fundamentals

This week’s section exercises focuses on exploring some C++ quirks and learning about strings. Have fun!

Each week, we will also be releasing a Qt Creator project containing starter code and testing infrastructure for that week's section problems. When a problem name is followed by the name of a .cpp file, that means you can practice writing the code for that problem in the named file of the Qt Creator project. Here is the zip of the section starter code:

📦 Starter project

1. References Available Upon Request

Topics: Reference parameters, range-based for loops

Reference parameters are an important part of C++ programming, but can take some getting used to if you’re not familiar with them. Trace through the following code. What does it print?

void maui(string s) {
    for (int i = 0; i < s.length(); i++) {
        s[i] += 2;
    }
}

void sina(string& s) {
    for (int i = 0; i < s.length(); i++) {
        s[i] += 2;
    }
}

void moana(string& s) {
    for (char ch : s) {
        ch += 2;
    }
}

void heihei(string& s) {
    for (char& ch : s) {
        ch += 2;
    }
}

string teFiti(string& s) {
    string result;
    for (char ch : s) {
        result += (ch + 2);
    }
    return result;
}

int main() {
    string s = "umm";

    maui(s);
    cout << s << endl;

    sina(s);
    cout << s << endl;

    moana(s);
    cout << s << endl;

    heihei(s);
    cout << s << endl;

    teFiti(s);
    cout << s << endl;

    return 0;
}

umm
woo
woo
yqq
yqq

2. Pig-Latin (piglatin.cpp)

Topics: Strings, reference parameters, return types

Write two functions, pigLatinReturn and pigLatinReference, that accept a string and convert said string into its pig-Latin form. To convert a string into pig-Latin, you must follow these steps:

• Split the input string into 2 strings: a string of characters BEFORE the first vowel, and a string of characters AFTER (and including) the first vowel.
• Append the first string (letters before the first vowel) to the second string.
• Append the string "ay" to the resulting string.

Here are a few examples…

sean -> eansay

julian -> ulianjay

You will need to write this routine in two ways: once as a function that returns the pig-Latin string to the caller, and once as a function that modifies the supplied parameter string and uses it to store the resulting pig-Latin string. These will be done in pigLatinReturn and pigLatinReference, respectively. You may assume that your input is always a one-word, all lowercase string with at least one vowel.

Here's a code example of how these functions differ…

string name = "julian";
string str1 = pigLatinReturn(name);
cout << str1 << endl; // prints "ulianjay"

pigLatinReference(name);
cout << name << endl; // prints "ulianjay"

Once you've written these functions, discuss with your section the benefits and drawbacks of these two approaches. Which do you feel is easier to write? Which do you think is more convenient for the caller? Do you think one is better style than the other?

// Use const because VOWELS won't change -- no need to declare repeatedly
// in isVowel.
const string VOWELS = "aeiouy";

// Helper function, which I'd highly recommend writing!
bool isVowel(char ch) {
    // A little kludgy, but the handout guarantees that
    // ch will ALWAYS be lower case :)
    // NOTE: For an assignment, you probably want a more robust isVowel.
    return VOWELS.find(ch) != string::npos;
}

string pigLatinReturn(string input) {
    int strOneIndex = 0;
    for (int i = 0; i < input.length(); i++) {
        if (isVowel(input[i])) {
            strOneIndex = i;
            break;
        }
    }
    string strOne = input.substr(0, strOneIndex);
    string strTwo = input.substr(strOneIndex);
    return strTwo + strOne + "ay";
}

void pigLatinReference(string &input) {
    int strOneIndex = 0;
    for (int i = 0; i < input.length(); i++) {
        if (isVowel(input[i])) {
            strOneIndex = i;
            break;
        }
    }
    string strOne = input.substr(0, strOneIndex);
    string strTwo = input.substr(strOneIndex);
    input = strTwo + strOne + "ay";
}

string pigLatin(const string &input);

3. Program analysis: C++isms you should know

Topics: Types, References, range based loops, strings, stanford C++ library

In the following, we will analyze a simple program that filters last names whose end match a specific substring. Given an input string of format:

name1,name2, ... 

and a string suffix, the program returns all the names in the input string that ends with the suffix.

#include "SimpleTest.h"
#include "vector.h"
#include "strlib.h"

using namespace std;

/*
   @param input: input string whose last names will be filtered
   @param suffix: the substring which we will filter last names by
   Functionality: this function filters the input string and returns last names
        that end with 'suffix'
*/
Vector<string> filter(string input, string suffix)
{
    Vector<string> filteredNames;
    Vector<string> names = stringSplit(input, ',');

    for (string name: names) {
        // convert to lowercase so we can easily compare the strings
        if (endsWith(toLowerCase(name), toLowerCase(suffix))) {
            filteredNames.add(name);
        }
    }
    return filteredNames;
}

STUDENT_TEST("Filter names") {
    Vector<string> results = filter("Zelenski,Szumlanski,Rodriguez Cardenas", "Ski");
    EXPECT_EQUAL(results, {"Zelenski","Szumlanski"});

    results = filter("AmbaTi,Szumlanski,Tadimeti", "TI");
    Vector<string> expected = {"AmbaTi", "Tadimeti"};
    EXPECT(results == expected);

    results = filter("Zelenski,Szumlanski,Rodriguez Cardenas", "nas");
    EXPECT_EQUAL(results, {"Rodriguez Cardenas"});

    results = filter("Szumlanski,Rodriguez Cardenas", "AaS");
    EXPECT_EQUAL(results, {});

    // what other tests could you add?
}

results = filter("Zelenski,Szumlanski,Rodriguez Cardenas", "uez");
EXPECT_EQUAL(results, {});

4. Returning and printing

Topics: Function call and return, return types

Below is a series of five printLyrics_v# functions, each of which has a blank where the return type should be. For each function, determine

• what the return type of the function should be,
• what value, if any, is returned, and
• what output, if any, will be produced if that function is called.

Is it appropriate for each of these functions to be named printLyrics? Why or why not?

_____ printLyrics_v1() {
    cout << "Havana ooh na na" << endl;
}
_____ printLyrics_v2() {
    return "Havana ooh na na";
}
_____ printLyrics_v3() {
    return "H";
}
_____ printLyrics_v4() {
    return 'H';
}
_____ printLyrics_v5() {
    cout << 'H' << endl;
}

void printLyrics_v1() {
    cout << "Havana ooh na na" << endl;
}

string printLyrics_v2() {
    return "Havana ooh na na";
}

string printLyrics_v3() {
    return "H";
}

char printLyrics_v4() {
    return 'H';
}

void printLyrics_v5() {
    cout << 'H' << endl;
}

* Setting up your environment correctly

Topics: QT Creator

• Navigate to Recommended Qt settings and set all recommended settings suggested. You'll use Qt Creator for all assignments this quarter, so it's important that you use the best settings to make you more efficient.
• Make a CS106B folder in your home directory. You can do so by:
  • Opening your finder(if you use a Mac) or Windows Explorer (if you use Windows)
  • Click on MacintoshHD for Mac or Primary Drive (C:) for windows
  • Click on Users
  • Click your name
  • Right click and make new folder.
  • Name the folder with ordinary characters, no spaces, special characters or emojis When you download new assignments and section materials, be sure to store them here. This will make it so that Qt has all the permissions it needs to run your programs
• If you use a Mac
  • Right click on this section's .pro file
  • Select Get info
  • Check that Qt Creator has been set as the default program to open .pro files. If not, choose Qt Creator from the drop down, and click on Change All
• If you use Windows
  • Open File Explorer (open any folder).
  • Click the View tab.
  • Select "File name extension" This will make it so you can see which files end with .pro
• Helpful Qt Creator hot keys (if you use windows, replace Command with Ctrl):
  • Command + B to build your program
  • Command + R to run your program
  • Command + Y to run in debug mode