在Poly/ML中从源代码字符串中获取解析树

Question

我正在尝试编译一个源代码字符串，并使用Poly/ML打印解析树。以下代码将进行编译，但解析树为空：

fun main () =
    let
        val stream = TextIO.openString "let val a = \"abc\"; val b = \"def\"; val c = a ^ b in print c end";
        val _ = PolyML.compiler (fn () => TextIO.input1 stream, []);
        val (_, parseTree) = !PolyML.IDEInterface.parseTree
    in
        PolyML.print (parseTree);
        PolyML.print (List.length parseTree);
        List.map PolyML.print (parseTree);
        ()
    end

运行以下命令：

$ ./a.out
[...]
0
$

我需要做什么才能从编译器中获得解析树？我还尝试了一个使用CPCompilerResultFun编译器参数的变体。但这也不起作用：

fun main () =
    let
        fun useTree (NONE, _) () =
            (PolyML.print "not parsed"; ())
          | useTree (SOME parseTree, _) () =
            (PolyML.print "parsed"; PolyML.print parseTree; ());

        val stream = TextIO.openString "let val a = \"abc\"; val b = \"def\"; val c = a ^ b in print c end";
        val _ = PolyML.compiler (fn () => TextIO.input1 stream, [PolyML.Compiler.CPCompilerResultFun useTree]);
    in
        ()
    end

运行此命令不会产生任何输出。

Answer 1

我能够通过提供PolyML.Compiler.CPCompilerResultFun编译器选项来获得它。它允许您access and save the parse tree。但是，关于解析树的实际表示方式，我不能说太多。有一些文档here (该网站对我来说已经关闭)，但我还不能理解它。

val resultTrees : PolyML.parseTree list ref = ref [];

fun compilerResultFun (parsetree, codeOpt) =
  let
    val _ =
      case parsetree of
        SOME pt => resultTrees := !resultTrees @ [pt]
      | NONE => ()
  in
    fn () => raise Fail "not implemented"
  end;

val stream = TextIO.openString "val a = 1";

val _ = PolyML.compiler (fn () => TextIO.input1 stream, [
  PolyML.Compiler.CPCompilerResultFun compilerResultFun
]);

val [(a, [PolyML.PTfirstChild b])] = !resultTrees;
val (_, [PolyML.PTfirstChild c, PolyML.PTparent d, PolyML.PTprint e]) = b ();