将OCaml AST打印为OCaml代码

Question

我有这段包含camlp4报价的代码.

let f_name = "my_func"
<:str_item< value $lid:f_name$ a = a * 2 >>

经过这个camlp4of,它产生了这个:

  Ast.StExp (_loc,
    (Ast.ExApp (_loc,
       (Ast.ExApp (_loc, (Ast.ExId (_loc, (Ast.IdLid (_loc, "=")))),
          (Ast.ExApp (_loc,
             (Ast.ExApp (_loc,
                (Ast.ExId (_loc, (Ast.IdLid (_loc, "value")))),
                (Ast.ExId (_loc, (Ast.IdLid (_loc, f_name)))))),
             (Ast.ExId (_loc, (Ast.IdLid (_loc, "a")))))))),
       (Ast.ExApp (_loc,
          (Ast.ExApp (_loc, (Ast.ExId (_loc, (Ast.IdLid (_loc, "*")))),
             (Ast.ExId (_loc, (Ast.IdLid (_loc, "a")))))),
          (Ast.ExInt (_loc, "2")))))))

我的问题是,无论如何打印生成的ocaml代码？我camlp4of应该使用什么命令或选项来显示代码？我希望从上面的例子中看到的是:

value my_func a = a * 2

那可能吗？原因是因为我想做一些调试,看看生成的ocaml代码是怎样的.

Answer 1

这是几天前我问自己的一个很好的问题.

您可以使用具有该类型的`Camlp4.PreCast.Printers.OCaml.print_implem

value print_implem : ?input_file:string -> ?output_file:string ->
                     Ast.str_item -> unit;

例如,在toplevel中(仅显示最后一个命令的输出):

# #use "topfind";;
# #require "camlp4";;
# #load "camlp4of.cma";;
# open Camlp4.PreCast;;
# let _loc = Loc.ghost;;
# let test =
    let f_name = "my_func" in
    <:str_item< value $lid:f_name$ a = a * 2 >>;;
# Printers.OCaml.print_implem test;;
let _ = (value my_func a) = (a * 2);;
- : unit = ()

另一个解决方案是创建一个语法扩展,它将产生您正在寻找的输出.例如,一个Camlp4AstFilter只会忽略它的输入,并返回你的东西作为输出,所以你可以camlp4of my_filter.cmo -str ''用来获得你正在寻找的AST.