Question

typedef struct leaf{
  int value;
  struct leaf* lchild;
  struct leaf* rchild;
} LEAF;

For example the one above defines structure leaf and makes 2 members of that type: lchild, rchild. So is this like a recursion?

Answer 1

Your assumption is wrong. leaf has 2 members of type leaf*, not leaf. So it’s not (data) recursion.

And the following

struct leaf
{
    leaf x;
};

would be illegal in C++. Note that in C++ you don’t need struct leaf when you declare a member of variable of that type, nor do you need the typedef.