C++ Notes

1 minute read

Published: September 03, 2024

I have largely evaded formally learning C++ by leveraging my knowledge of C to pattern match on existing C++ codebases, or using Rust in my own green-field projects. Nevertheless, it seems that knowing C++ is pretty important given that everyone still uses it and test on its concepts in interviews. I guess I cannot possibly continue on without knowing what a virtual method call is.

A previous company shipped me a copy of “A Tour of C++, Third Edition” by Bjarne Stroustrup. I’ll be dumping my notes here so I actually remember stuff.

class Vector {
public:
    Vector(int s) :elem{new double[s]}, sz{s} {}
    double& operator[](int i) { return elem[i]; }
    int size() { return sz; }
private:
    double* elem;
    int sz;
};

int main() {
    Vector v(6);
}

enum class Color { red, green, blue };

export module vector_printer;

import std;

export template<typename T> void print(std::vector<T>& v)
{
    cout << "{\n";
    for (const T& val : v) {
        std::cout << " " << val << '\n';
    }
    cout << "}\n";
}

polymorphism

using namespace std;

class base {
public:
    virtual void print() { cout << "print base class\n"; }
    void show() { cout << "show base class\n"; }
};

class derived : public base {
public:
    void print() { cout << "print derived class\n"; }
    void show() { cout << "show derived class\n"; }
};

int main()
{
    base* bptr;
    derived d;
    bptr = &d;
 
    // Virtual function, binded at runtime
    bptr->print();
 
    // Non-virtual function, binded at compile time
    bptr->show();
 
    return 0;
}

% Output
print derived class
show base class

Basically when you declare a class’s method as virtual, you are ensuring that sub-classes use their own implementation. Aka, override-able functions.

Brian E. Zhang