将 Coq 提取到 Haskell，同时保留注释

Question

在将 Coq 提取到 Haskell 时是否可以保留注释？理想情况下，我希望机器生成的 Haskell 文件不被人类修改，因此提取评论的动机很明确。但是，我找不到如何去做，我想知道这是否完全可能（？）。这是一个示例 Coq 文件：

(*************)
(* factorial *)
(*************)
Fixpoint factorial (n : nat) : nat :=
  match n with
  | 0 => 1
  | 1 => 1 (* this case is redundant *)
  | S n' => (mult n (factorial n'))
  end.

Compute (factorial 7).

(********************************)
(* Extraction Language: Haskell *)
(********************************)
Extraction Language Haskell.

(***************************)
(* Extract to Haskell file *)
(***************************)
Extraction "/home/oren/Downloads/RPRP/output.hs" factorial.

当我将它提取到 Haskell 时，除了 factorial 中的注释丢失之外，一切正常：

$ coqc ./input.v > /dev/null
$ cat ./output.hs
module Output where

import qualified Prelude

data Nat =
   O
 | S Nat

add :: Nat -> Nat -> Nat
add n m =
  case n of {
   O -> m;
   S p -> S (add p m)}

mul :: Nat -> Nat -> Nat
mul n m =
  case n of {
   O -> O;
   S p -> add m (mul p m)}

factorial :: Nat -> Nat
factorial n =
  case n of {
   O -> S O;
   S n' ->
    case n' of {
     O -> S O;
     S _ -> mul n (factorial n')}}

Answer 1

不，这不可能。仔细检查，您可以看到 the AST for the internal language that extraction targets, called MiniML, doesn't (as of v8.9) have any constructors for comments. The relevant file is in the Coq repository, plugins/extraction/miniml.ml.

将 Coq 提取到 Haskell，同时保留注释

Extracting Coq to Haskell while keeping comments

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