我有以下語法,我想解析輸入以獲得關聯的AST。 ANTLR for Java一切都很簡單。由於ANTLR4,在語法文件中,您不必指定選項`output = AST;獲取AST信息。與Python一起使用ANTLR與代碼從Java遷移
Hello.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));
}
}
的輸出將是:
(expr (atom 5) (op +) (atom 3))
但是,請你告訴我如何獲得與Python實現相同的結果?目前,我正在使用ANTLR 3.1.3 Runtime for Python。下面的代碼只返回 「(+ 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()
嗯,真可惜!無論如何謝謝你的信息。 :) – anhldbk