Match or generate a sequence of Element. This predicate is
deterministic if List is fully instantiated and Element is
deterministic. When parsing, this predicate is gready and does not
prune choice points. For example:
?- phrase(sequence(digit, Digits), `123a`, L).
Digits = "123",
L = [97] ;
Digits = [49, 50],
L = [51, 97] ;
...