Dicebot:
std.typecons.Tuple is just a subset of all structs implementing
specific behavior. It still acts as struct everywhere when
applicable.
A subset is not the same as the whole set.
You are missing something important about what a data structure
is. Take a look at your computer science books.
Another example: a dynamic array allows several operations,
including append at the end and pop from the end. If I define a
Stack data structure based on a dynamic array with just its
pop/append/empty/length operations, I have defined a new data
structure.
Bye,
bearophile