可视化使用 ANTLR 创建的 AST(在 .Net 环境中) [英] Visualizing an AST created with ANTLR (in a .Net environment)

问题描述

对于一个宠物项目，我开始使用 ANTLR.在学习了一些教程之后，我现在正在尝试为我自己的语言创建语法并生成 AST.

For a pet project I started to fiddle with ANTLR. After following some tutorials I'm now trying to create the grammar for my very own language and to generate an AST.

现在我主要是在 ANTLRWorks 里乱搞，但现在我已经验证了解析树似乎没问题(反复地，因为我仍在学习，仍然需要做出一些关于树的最终结构)创建 AST.似乎 antlrworks 不会将它可视化(或者至少不使用解释器"功能，调试在我的任何机器上都不起作用).

For now I'm messing around in ANTLRWorks mostly, but now that I have validated that the parse tree seems to be fine I'd like to (iteratively, because I'm still learning and still need to make some decisions regarding the final structure of the tree) create the AST. It seems that antlrworks won't visualize it (or at least not using the "Interpreter" feature, Debug's not working on any of my machines).

底线:是手动方式可视化 AST、遍历/显示它或将树以字符串表示形式打印到控制台的唯一方法吗?

Bottom line: Is the only way to visualize the AST the manual way, traversing/showing it or printing the tree in string representation to a console?

我正在寻找的是一种从输入、语法到>视觉 AST 表示以及 ANTLRWorks 的解释器"功能的简单方法.有什么想法吗?

What I'm looking for is a simple way to go from input, grammar -> visual AST representation a la the "Interpreter" feature of ANTLRWorks. Any ideas?

推荐答案

正确，解释器只显示解析过程中使用了哪些规则，而忽略任何 AST 重写规则.

Correct, the interpreter only shows what rules are used in the parsing process, and ignores any AST rewrite rules.

你可以做的是使用 StringTemplate 来创建一个 Graphviz DOT 文件.创建这样一个DOT-file后，您可以使用一些第三方查看器来显示这棵树(图).

What you can do is use StringTemplate to create a Graphviz DOT-file. After creating such a DOT-file, you use some 3rd party viewer to display this tree (graph).

这是一个 Java 快速演示(我对 C# 了解很少，抱歉).

Here's a quick demo in Java (I know little C#, sorry).

采用以下生成 AST 的(过于简单的)表达式语法:

Take the following (overly simplistic) expression grammar that produces an AST:

grammar ASTDemo;

options { 
  output=AST; 
}

tokens {
  ROOT;
  EXPRESSION;
}

parse
  :  (expression ';')+ -> ^(ROOT expression+) // omit the semi-colon
  ;

expression
  :  addExp -> ^(EXPRESSION addExp)
  ;

addExp
  :  multExp
     ( '+'^ multExp
     | '-'^ multExp
     )*
  ;

multExp
  :  powerExp
     ( '*'^ powerExp
     | '/'^ powerExp
     )*
  ;

powerExp
  :  atom ('^'^ atom)*
  ;

atom
  :  Number
  |  '(' expression ')' -> expression // omit the parenthesis
  ;

Number
  :  Digit+ ('.' Digit+)?
  ;

fragment
Digit
  :  '0'..'9'
  ;

Space
  :  (' ' | '\t' | '\r' | '\n') {skip();}
  ;

首先让 ANTLR 从中生成词法分析器和解析器文件:

First let ANTLR generate lexer and parser files from it:

java -cp antlr-3.2.jar org.antlr.Tool ASTDemo.g 

然后创建一个小的测试工具来解析表达式 "12 * (5 - 6); 2^3^(4 + 1);" 并将输出一个 DOT 文件:

then create a little test harness that parses the expressions "12 * (5 - 6); 2^3^(4 + 1);" and will output a DOT-file:

import org.antlr.runtime.*;
import org.antlr.runtime.tree.*;
import org.antlr.stringtemplate.*;

public class MainASTDemo {
    public static void main(String[] args) throws Exception {
        ANTLRStringStream in = new ANTLRStringStream("12 * (5 - 6); 2^3^(4 + 1);");
        ASTDemoLexer lexer = new ASTDemoLexer(in);
        CommonTokenStream tokens = new CommonTokenStream(lexer);
        ASTDemoParser parser = new ASTDemoParser(tokens);
        ASTDemoParser.parse_return returnValue = parser.parse();
        CommonTree tree = (CommonTree)returnValue.getTree();
        DOTTreeGenerator gen = new DOTTreeGenerator();
        StringTemplate st = gen.toDOT(tree);
        System.out.println(st);
    }
}

编译所有.java文件:

// *nix & MacOS
javac -cp .:antlr-3.2.jar *.java

// Windows
javac -cp .;antlr-3.2.jar *.java

然后运行主类并将其输出通过管道传输到名为 ast-tree.dot 的文件:

and then run the main class and pipe its output to a file named ast-tree.dot:

// *nix & MacOS
java -cp .:antlr-3.2.jar MainASTDemo > ast-tree.dot

// Windows
java -cp .;antlr-3.2.jar MainASTDemo > ast-tree.dot

文件 ast-tree.dot 现在包含:

digraph {

    ordering=out;
    ranksep=.4;
    bgcolor="lightgrey"; node [shape=box, fixedsize=false, fontsize=12, fontname="Helvetica-bold", fontcolor="blue"
        width=.25, height=.25, color="black", fillcolor="white", style="filled, solid, bold"];
    edge [arrowsize=.5, color="black", style="bold"]

  n0 [label="ROOT"];
  n1 [label="EXPRESSION"];
  n1 [label="EXPRESSION"];
  n2 [label="*"];
  n2 [label="*"];
  n3 [label="12"];
  n4 [label="EXPRESSION"];
  n4 [label="EXPRESSION"];
  n5 [label="-"];
  n5 [label="-"];
  n6 [label="5"];
  n7 [label="6"];
  n8 [label="EXPRESSION"];
  n8 [label="EXPRESSION"];
  n9 [label="^"];
  n9 [label="^"];
  n10 [label="^"];
  n10 [label="^"];
  n11 [label="2"];
  n12 [label="3"];
  n13 [label="EXPRESSION"];
  n13 [label="EXPRESSION"];
  n14 [label="+"];
  n14 [label="+"];
  n15 [label="4"];
  n16 [label="1"];

  n0 -> n1 // "ROOT" -> "EXPRESSION"
  n1 -> n2 // "EXPRESSION" -> "*"
  n2 -> n3 // "*" -> "12"
  n2 -> n4 // "*" -> "EXPRESSION"
  n4 -> n5 // "EXPRESSION" -> "-"
  n5 -> n6 // "-" -> "5"
  n5 -> n7 // "-" -> "6"
  n0 -> n8 // "ROOT" -> "EXPRESSION"
  n8 -> n9 // "EXPRESSION" -> "^"
  n9 -> n10 // "^" -> "^"
  n10 -> n11 // "^" -> "2"
  n10 -> n12 // "^" -> "3"
  n9 -> n13 // "^" -> "EXPRESSION"
  n13 -> n14 // "EXPRESSION" -> "+"
  n14 -> n15 // "+" -> "4"
  n14 -> n16 // "+" -> "1"

}

可以通过此处的查看者之一查看.甚至还有在线观众.以这个为例:https://dreampuf.github.io/GraphvizOnline/

which can be viewed with one of the viewers here. There are even online viewers. Take this one for example: https://dreampuf.github.io/GraphvizOnline/

当给它输入ast-tree.dot的内容时，会产生下图:

When feeding it the contents of ast-tree.dot, the following image is produced:

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