将ANTLR与Python结合使用,代码从Java迁移而来

将ANTLR与Python结合使用,代码从Java迁移而来,antlr,abstract-syntax-tree,parse-tree,Antlr,Abstract Syntax Tree,Parse Tree,我有以下语法,我想解析输入以获得相关的AST。使用ANTLR for Java,一切都很简单。由于ANTLR4,在语法文件中,您不必指定选项`output=AST;获取ASTs信息 你好.g grammar Hello; // Define a grammar called Hello stat : expr NEWLINE | ID '=' expr NEWLINE | NEWLINE | expr ;

我有以下语法,我想解析输入以获得相关的AST。使用ANTLR for Java,一切都很简单。由于ANTLR4,在语法文件中,您不必指定选项`output=AST;获取ASTs信息

你好.g

grammar  Hello; //  Define  a  grammar  called  Hello
stat    :   expr NEWLINE       
    |   ID '=' expr NEWLINE 
    |   NEWLINE   
        | expr
    ;

expr:   atom (op atom)* ;

op  : '+'|'-' ;

atom    :   INT |   ID;

ID  :   [a-zA-Z]+ ;

INT :  [0-9]+ ;

NEWLINE :   '\r' ? '\n' ;

WS  :   [ \t\r\n]+ -> skip ;
Test.java

import  org.antlr.v4.runtime.*;
import  org.antlr.v4.runtime.tree.*;
import java.io.*;
import lib.HelloLexer;
import lib.HelloParser;
public class Test {
    public  static  void  main(String[]  args)  throws  Exception  {
        ANTLRInputStream  input  =  new  ANTLRInputStream("5 + 3");
        //  create  a  lexer  that  feeds  off  of  input  CharStream
        HelloLexer  lexer  =  new  HelloLexer(input);
        //  create  a  buffer  of  tokens  pulled  from  the  lexer
        CommonTokenStream  tokens  =  new  CommonTokenStream(lexer);
        //  create  a  parser  that  feeds  off  the  tokens  buffer
        HelloParser  parser  =  new  HelloParser(tokens);
        ParseTree  tree  =  parser.expr();  //  begin  parsing  at  init  rule
        //System.out(tree.toStringTree(parser));  //  print  LISP-style  tree
        System.out.println(tree.toStringTree(parser));
    }   
}
输出将为:

(expr (atom 5) (op +) (atom 3))
但是您能告诉我如何通过Python实现获得相同的结果吗?目前,我正在使用ANTLR 3.1.3 Python运行时。以下代码仅返回“(+5 3)”

Test.py

import sys
import antlr3
import antlr3.tree
from antlr3.tree import Tree
from HelloLexer import *
from HelloParser import *

char_stream = antlr3.ANTLRStringStream('5 + 3')
lexer = ExprLexer(char_stream)
tokens = antlr3.CommonTokenStream(lexer)
parser = ExprParser(tokens)
r = parser.stat()

print r.tree.toStringTree()

Antlr4目前没有Python目标,Antlr3也不支持自动生成解析树来生成您正在查看的输出


您可能可以使用ANTLR 3中的AST创建功能来生成树,但它的形式(当然不是简单的)与ANTLR 4不同。

Python现在有一个ANTLR 4运行时(),但ToString树是Python运行时中的一个类方法。您可以这样调用它以获得包含字符串化标记的lisp样式解析树:

from antlr4 import *
from antlr4.tree.Trees import Trees
# import your parser & lexer here

# setup your lexer, stream, parser and tree like normal

print(Trees.toStringTree(tree, None, parser))

# the None is an optional rule names list