Final answer:
The statement is true; OCaml implements lists as variants, distinguishing between the empty list and cons cells, representing a common use of algebraic data types.
Step-by-step explanation:
The statement "OCaml just codes up lists as variants" is True. In OCaml, lists are indeed implemented as variants. A list is either an empty list, represented by [], or it is a cons cell, which contains a head element and a tail that points to the remainder of the list, represented by x::xs where x is the head element and xs is the tail of the list. This can be understood as a recursive variant data type, with the empty list as the base case and the cons cell as the recursive case that builds up the list. For example, the list [1; 2; 3] is constructed as 1::(2::(3::[])) in OCaml. This implementation showcases the power of algebraic data types in OCaml, allowing for the concise and clear definition of potentially complex data structures.