> Because tuples are generally immutable, there is little semantic
> difference, but the compiler does have to keep track of which is which.

Thanks, but which differnce ?

>In most cases I would guess that 'A' would be more efficient (unless there
are
> lots of larger constructors sharing the same tuple).
Peraps in patter mathching:

# type t = A of int*int | B of (int*int);;
type t = A of int * int | B of (int * int)

# fun x -> match x with A (a,b) -> (a,b) | B a -> a;;
- : t -> int * int = <fun>

where the case of B will be more efficient since the are not need to rebuild
a pair

Best,
FG