[Caml-list] short-circuit in Real World Ocaml ch 3 deserves a comment

[Jean Saint-Remy <jeansaintremy@yahoo.com>]

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Hi,

I found a missing "does not change" sentence fragment in the third section on Lists and Patterns


"Each:: essentially adds a new block to the proceding picture. Such a block contains two things: a reference to the data in that list element, and a reference to the remainder of the list. This is why :: can extend a list without modifying it; extension allocates a new list element but {here} change any of the existing ones, as you can see: "


The example code using pattern matching appears to be a "let rec" short-circuit which I believe deserves a comment in the book. It appears to be puzzling, we are binding a "zero" to the head of the list in order to drop it? I think it is a fine example of OCaml that should be encouraged, not just an isolated case.

let rec drop_zero ls = match ls with
  | [] -> [] 

  | 0 :: tl -> drop_zero tl
  | hd :: tl -> hd :: drop_zero tl 

;;

With kind regards,

Jean

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