C++ Tutorial 3
As we continue to learn C++ through problem solving we cover Functions, Pointers, Local Variables, how to create a range function and solve a bunch of problems.
I hope you find using pointers to be a breeze after this tutorial. Please share your alternative problem solutions. All of the code and a transcript follows the video below.
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Cheat Sheet / Transcript
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// ---------- C++ Tutorial 3 ---------- std::vector<int> myVec(10); // Generates incremental values starting at 0 and places // them in the vector provided // begin points at the 1st index and end points at the last // in the vector std::iota(std::begin(myVec), std::end(myVec), 0); // We can output the vector using a standard for loop for(int i = 0; i < myVec.size(); ++i){ std::cout << myVec[i] << "\n"; } // An abbreviated for loop is also available // auto determines the data type based on the value // y is assigned each value in the vector incrementing // the index by 1 each time through the loop for(auto y: myVec) std::cout << y << "\n"; // Find if a value is even / odd with modulus int val = 8; if((val % 2) == 0){ std::cout << val << " is Even\n"; } else { std::cout << val << " is Odd\n"; } // ----- PROBLEM : GENERATE VECTOR (1 - 10) AND PRINT EVENS ----- std::vector<int> myVec2(10); std::iota(std::begin(myVec2), std::end(myVec2), 1); // We can print just even numbers with modulus for(auto y: myVec2){ if((y % 2) == 0) std::cout << y << "\n"; } // ----- END OF PROBLEM ----- #include <cstdlib> #include <iostream> #include <string> #include <vector> #include <sstream> // Needed for std::iota #include <numeric> // ----- FUNCTION PROTOTYPES ----- // You define the return type and data types for functions // using a function prototype so main knows what is to be expected // from this function double AddNumbers(double num1, double num2); void AssignName(); void AssignAge(int age); int AssignAge2(int age); // This function receives pointers void AssignAge3(int* pAge); // Double values in array passed void DoubleArray(int *arr, int size); // ----- END OF FUNCTION PROTOTYPES ----- int main() { // ----- FUNCTIONS ----- // Code that gets above 8 to 10 lines should be broken off // into a separate function to better organize your code // and to promote reuse double num1, num2; std::cout << "Enter Num 1 : "; // An alternative way to store a value std::cin >> num1; std::cout << "Enter Num 2 : "; std::cin >> num2; // Call the function printf("%.1f + %.1f = %.1f\n", num1, num2, AddNumbers(num1, num2)); // Variables in a function are local to that function // Undeclared identifier error // std::cout << name; // Variables values changed in a function don't // translate globally int age = 43; AssignAge(age); std::cout << "New Age " << age << "\n"; // You could change the value by passing it back age = AssignAge2(age); std::cout << "New Age " << age << "\n"; // A Pointer stores a address in memory // You declare a pointer to be of the same type as the data // type to which it points // If you are storing the address of an int then the // pointer is an int // When you declare a pointer give it a null value int* pAge = NULL; // The reference operator returns the address for a // variable that can be stored in a pointer pAge = &age; // Print the address Hexidecimal Number std::cout << "Address : " << pAge << "\n"; // Get the value at that address with the dereference operator std::cout << "Value at Address : " << *pAge << "\n"; // We can create a pointer to an array and cycle through // the data with ++ and -- int intArray[] = {1,2,3,4}; int* pIntArray = intArray; std::cout << "1st " << *pIntArray << " Address " << pIntArray << "\n"; pIntArray++; std::cout << "2nd " << *pIntArray << " Address " << pIntArray << "\n"; pIntArray--; std::cout << "1st" " " << *pIntArray << " Address " << pIntArray << "\n"; // You can pass a pointer to a function and then the function // can change that variables value globally age = 43; // Send the address for age to the function AssignAge3(&age); std::cout << "Pointer Age " << age << "\n"; // Create an array and double values int arr[] = {1,2,3,4}; DoubleArray(arr, 4); for(int i = 0; i < 4; ++i){ std::cout << "Array " << arr[i] << "\n"; } return 0; } // ----- FUNCTIONS ----- // A function starts with the data type it will return or void // if no value is returned // You also list the data types for the parameters passed into // a function and you may assign them default values double AddNumbers(double num1 = 0, double num2 = 0){ return num1 + num2; } // A variable created inside a function can't be accessed // outside of it void AssignName(){ std::string name = "Derek"; } void AssignAge(int age){ age = 24; } int AssignAge2(int age){ age = 24; return age; } // Function that receives a pointer void AssignAge3(int* pAge){ // Use dereference operator to change the value at the address *pAge = 22; } // Double values in array void DoubleArray(int *arr, int size){ for(int i = 0; i < size; ++i){ arr[i] = arr[i] * 2; } } // ----- FUNCTIONS ----- #include <cstdlib> #include <iostream> #include <string> #include <vector> std::vector<int> Range(int start, int max, int step); int main() { // ----- PROBLEM CREATE A RANGE FUNCTION ----- // Create a function that receives a starting value, // max value and an increment amount between // values and receive a vector in return std::vector<int> range = Range(1, 10, 2); // Cycle through the vector for(auto y: range){ std::cout << y << "\n"; } // ----- END PROBLEM CREATE A RANGE FUNCTION ----- // ----- PROBLEM CALCULATE COMPOUNDING INTEREST ----- double investment = 0.0; double interestRate = 0.0; std::cout << "How much to invest : "; std::cin >> investment; std::cout << "Interest Rate : "; std::cin >> interestRate; // Convert to a percent interestRate *= .01; for(auto y: Range(1,10,1)){ investment = investment + (investment * interestRate); } std::cout << "Value after 10 years : " << investment << "\n"; // ----- END PROBLEM CALCULATE COMPOUNDING INTEREST ----- return 0; } std::vector<int> Range(int start, int max, int step){ // Every while statement needs an index to start with int i = start; // Will hold returning vector std::vector<int> range; // Make sure we don't go past max value while(i <= max){ // Add value to the vector range.push_back(i); // Increment the required amount i += step; } return range; } // ---------- End of C++ Tutorial 3 ---------- |
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