Hey everyone! I'm diving into C++ and I'm really struggling with some code involving structs and constructors. Here's what I'm looking at:
```cpp
struct vertex {
float x, y, z;
float& operator[](size_t i) { return *(&x + i); }
};
struct triangle {
std::array vertices{};
triangle() = default;
triangle(std::array arr) : vertices(std::move(arr)) {}
triangle(std::array arr) {
for (int i = 0; i < 9; i++) {
vertices[i / 3][i % 3] = arr[i];
}
}
vertex& operator[](size_t i) { return vertices[i]; }
};
```
I'm particularly confused about this line: `float& operator[](size_t i) { return *(&x + i); }`. I get that `float` is the type and `&` refers to a reference, but I'm not sure what's happening overall. Is this a function definition?
Also, lines 6 to 12 are really confusing. I learned that structs were an early form of objects, but why are we defining functions inside them? What does `default` mean here? Any insights on structs or constructors in C++ would be super helpful!
1 Answer
You're spot on with wanting to understand object-oriented programming better! In C++, structs are quite similar to classes; they can have both data members and member functions. Your line `float& operator[](size_t i)` is indeed defining a member function. This is an example of operator overloading, which lets you access the `vertex` data like an array. Just remember that this particular implementation can lead to undefined behavior, depending on how memory is aligned for the struct.
Regarding the `triangle` struct, the `default` keyword is handy—it tells the compiler to provide a default constructor. Your constructors are used to initialize instances of the struct in different ways, which is a neat way to define flexibility in how you create your objects! If this feels overwhelming, a good starting point is to read some simpler examples or tutorials on C++ OOP concepts.
Thanks for the clarification! So, if I understand correctly, constructors in C++ are somewhat similar to class constructors in JavaScript, where properties are tied to `this` during initialization. That's really helpful! I'll check out those tutorials for sure.