add CList.extract_first

we already have
  val remove_first : ('a -> bool) -> 'a list -> 'a list
  (** Remove the first element satisfying a predicate, or raise [Not_found] *)
now we also have the more general
  val extract_first : ('a -> bool) -> 'a list -> 'a list * 'a
  (** Remove and return the first element satisfying a predicate,
      or raise [Not_found] *)

The implementation is tail-recursive. The code I'm hoping to factorize
reimplements extract_first in a tail-recursive way, so it seemed good
to preserve this. On the other hand remove_first is not tail-recursive
itself, and that gives better constant factors in real-life
cases. It's unclear what is the best choice.

0 files changed, 0 insertions, 0 deletions