Functions Part 1
Video
Key Takeways
Video Addendum
Its possible to create a variable without assigning to it. In that case the value of the variable is unknown. We represent this using a ? in our memory table.
For example:
#include <iostream>
int main() {
int x;
std::cout << "The initial value of X is: " << x << std::endl;
x = 100;
std::cout << "The final value of X is: " << x << std::endl;
return 0;
}
There’s no gaurantee what the initial value of X is. It might be 0, it might be 1234, or any other number. Hence why we refer to it as a ? in our memory table when we create the variable using int x;. If we had done int x = 100; Then we would have created it with the value of 100 assigned to it. Its perfectly valid to have a variable not have an initial value if you’ll be filling it in later either from user input or another function.
BUT, if you ever find you are reading from a value that is a ? in your memory table, you probably have a bug in your code!
Assignment
- For each code sample (0 to 2):
- Walk through the memory table for each example.
- Write down what you think each sample does (in complete sentences).
- Execute the code in a repl to validate your assumption. What was wrong / right about your step 2?
- Could we have used better naming to improve our code? How could we have done that?
- For each code sample (3 to 4):
- Describe what you think is wrong with the code (This means write it down in complete sentences!).
- Confirm your hypothesis by building a memory table
- Double check your work by trying to run the code in an example Repl.
- For your last 5-number calculator assignment, are there any places you can use functions?
- If so, create a new repl that does the exact same task but uses functions. Write down why you created the functions you did.
- If not, describe why you aren’t able to use functions.
- For code sample 5:
- Just by reading the code, what is your best guess as to what this code does?
- You’re welcome to play around with it in your repl to explore it.
- Note, we haven’t yet covered how to do memory tables for this, but we will in the following lesson.
Code Samples
Sample 0
#include <iostream>
int function1() {
std::cout << "Enter a number: ";
int a;
std::cin >> a;
return a;
}
int main() {
int A = function1();
if (A % 3 == 0) {
std::cout << "Fizz";
}
if (A % 5 == 0) {
std::cout << "Buzz";
}
if (A % 3 > 0) {
if (A % 5 > 0) {
std::cout << A;
}
}
std::cout << std::endl;
return 0;
}
Sample 1
#include <iostream>
float functionB() {
std::cout << "Enter a number: ";
float a;
std::cin >> a;
return a;
}
float functionA() {
std::cout << "Enter a number: ";
float a;
std::cin >> a;
std::cout << "Enter a number: ";
float b;
std::cin >> b;
return (a + b) / 2.0;
}
float functionC() {
std::cout << "Enter just 1 number? [y/n] ";
char a;
std::cin >> a;
if (a == 'y') {
return functionB();
std::cout << "Only gave you one number!" << std::endl;
}
if (a == 'n') {
return functionA();
}
std::cout << "Wasn't that fun?" << std::endl;
}
int main() {
float r = functionC();
std::cout << "Your final result is: " << r << std::endl;
return 0;
}
Sample 2
#include <iostream>
int functionA() {
std::cout << "Enter a number 0-5? ";
int a;
std::cin >> a;
return a;
}
int functionB() {
int b = functionA();
if (b < 0) {
return -1;
}
if (b >= 5) {
return -2;
}
return b;
}
int functionC() {
int c = functionB();
if (c < 0) {
return -c;
}
std::cout << "The " << c;
if (c == 1) {
std::cout << "st";
}
if (c != 1) {
if (c == 2) {
std::cout << "nd";
}
if (c != 2) {
if (c == 3) {
std::cout << "rd";
}
if (c != 3) {
std::cout << "th";
}
}
}
char l;
if (c == 0) {
l = 'a';
}
if (c == 1) {
l = 'e';
}
if (c == 2) {
l = 'i';
}
if (c == 3) {
l = 'o';
}
if (c == 4) {
l = 'u';
}
std::cout << " vowel is " << l << std::endl;
return 0;
}
int main() {
int status = functionC();
if (status == 1) {
std::cout << "The number was too small! Try again." << std::endl;
status = 1;
}
if (status == 2) {
std::cout << "The number was too big! Try again" << std::endl;
}
return status;
}
Sample 3
#include <iostream>
int function1() {
std::cout << "Enter a number: ";
int user_input;
std::cin << user_input;
return user_input;
}
int main() {
int user_input = function1();
std::cout "You entered user_input. Which is ";
if (user_input % 2 == 0) {
std::cout << "even";
}
if (user_input % 2 == 1) {
std::cout << "odd";
}
std::cout >> std::endl;
return 0;
}
Sample 4
#include <iostream>
int main() {
char user_input = function1();
if (user_input == 'V') {
std::cout << "You guessed my first initial!" << std::endl;
}
if (user_input == G) {
std::cout << "You guessed my last initial!" << std::endl;
}
std::cout << "You didn't guess anything correctly, try again!" << std::endl;
return 0;
}
char functionA() {
std::cout << "Enter a letter: ";
char letter;
std::cin >> letter;
return letter;
}
Sample 5
#include <iostream>
int functionA() {
std::cout << "Enter a number 0-5? ";
int a;
std::cin >> a;
return a;
}
bool functionB(int value) {
if (value < 0) {
return false;
}
if (value >= 5) {
return false;
}
return true;
}
int functionC(int value) {
std::cout << "The " << value;
if (value == 1) {
std::cout << "st";
}
if (value != 1) {
if (value == 2) {
std::cout << "nd";
}
if (value != 2) {
if (value == 3) {
std::cout << "rd";
}
if (value != 3) {
std::cout << "th";
}
}
}
char l;
if (value == 0) {
l = 'a';
}
if (value == 1) {
l = 'e';
}
if (value == 2) {
l = 'i';
}
if (value == 3) {
l = 'o';
}
if (value == 4) {
l = 'u';
}
std::cout << " vowel is " << l << std::endl;
return 0;
}
int main() {
int number = functionA();
bool valid = functionB(number);
if (!valid) {
std::cout << "This number won't work!" << std::endl;
return 1;
}
int status = functionC(number);
return status;
}
End of Assignment Checklist
- I finished all the assignments.
- I shared my assignments with others.
- I provided feedback for assignments of at least 2 others.
- I addressed the feedback from others and thanked them for the review.