lvalue vs. rvalue
- An lvalue is usually on the left side of an assignment and is addressable in the memory.
- An rvalue is usually on the right side of an assignment and isn’t addressable in the memory.
int i = 42; // i is an lvalue and 42 an rvalue int& j = i; // j is an lvalue reference
rvalue vs. universal reference
void f(int&& i); // no type deduction --> rvalue reference template<typename T> void f(T&& t); // type deduction --> universal reference
class vs. struct
- The members of a class per default are private.
- The members of a struct per default are public.
Deep vs. Shallow copy
- Deep: Copies the whole object. (e.g. std::vector)
- Shallow: Copies just the meta block. (e.g. std::shared_ptr)
- Mixed: std::vector<std::shared_ptr>
const std::string& vs. std::string_view
Both are ways to pass strings around, without copying them.
- const std::string&: Old-school (since C++98); Works just for std::string.
- std::string_view: New-school (since C++17); Works for any range of characters.
Prefer using std::string_view if possible.
const std::function& vs. std::function_ref
Both are ways to pass functions around, without copying them.
- const std::function&: Old-school (since C++11); Works with every callable type.
- std::function_ref: New-school (since C++26); Doesn’t work for lambdas with captures.
Prefer using std::function_ref if possible.