car/cdr have historic origin all the way back to the fifties. It made sense when creating the languages for familiarity. In essence it's a pair of data and can

car/cdr have historic origin all the way back to the fifties. It made sense when creating the languages for familiarity. In essence it's a pair of data and can be used in any which way you feel like. Understanding that makes for a powerful tool, which is why many functional experts so stubbornly hang on to them. Many functional languages have types as a first class citizen, and you can define abstractions on top of what you already have. If you put a cons cell as the data, you have created a tree structure as an example where car points children of a node and cdr points to the next sibling of a node.