这个示例 ANTLR 3 Python 语法有什么问题?
题
我正在尝试学习使用 ANTLR,并且在遵循此“教程”时似乎遇到了错误:https://theantlrguy.atlassian.net/wiki/display/ANTLR3/五+分钟+介绍+to+ANTLR+3
本质上,我创建了文件 SimpleCalc.g:
grammar SimpleCalc;
options {
language = Python;
}
tokens {
PLUS = '+' ;
MINUS = '-' ;
MULT = '*' ;
DIV = '/' ;
}
@header {
import sys
import traceback
from SimpleCalcLexer import SimpleCalcLexer
}
@main {
def main(argv, otherArg=None):
char_stream = ANTLRFileStream(sys.argv[1])
lexer = SimpleCalcLexer(char_stream)
tokens = CommonTokenStream(lexer)
parser = SimpleCalcParser(tokens);
try:
parser.expr()
except RecognitionException:
traceback.print_stack()
}
/*------------------------------------------------------------------
* PARSER RULES
*------------------------------------------------------------------*/
expr : term ( ( PLUS | MINUS ) term )* ;
term : factor ( ( MULT | DIV ) factor )* ;
factor : NUMBER ;
/*------------------------------------------------------------------
* LEXER RULES
*------------------------------------------------------------------*/
NUMBER : (DIGIT)+ ;
WHITESPACE : ( '\t' | ' ' | '\r' | '\n'| '\u000C' )+ { $channel = HIDDEN; } ;
fragment DIGIT : '0'..'9' ;
当我运行 ANTLR 工具时
java -classpath antlr-3.1.3.jar antlr.Tool SimpleCalc.g
我收到错误,从第一行开始:
ANTLR Parser Generator Version 2.7.7 (20060906) 1989-2005
SimpleCalc.g:2:1: unexpected token: grammar
error: Token stream error reading grammar(s):
SimpleCalc.g:15:1: unexpected char: '@'
SimpleCalc.g:2:1: rule grammar trapped:
SimpleCalc.g:2:1: unexpected token: grammar
TokenStreamException: unexpected char: '@'
这让我相信我在做一些愚蠢的事情,但我不确定是什么。
解决方案
你用错了 Tool
类来生成词法分析器和解析器。大多数 ANTLR 3.x 版本仍然与旧的 v2.7 版本有依赖关系,因此它包含在 v3.x 中。这 Tool
v2.7 中的类被称为 antlr.Tool
, ,而 v3.x 版本称为 org.antlr.Tool
. 。后者是您应该使用的:
java -classpath antlr-3.1.3.jar org.antlr.Tool SimpleCalc.g
编辑
这是一个基于 Wiki 语法的小演示,但随后添加了一些用于计算表达式的 Python 代码:
grammar SimpleCalc;
options {
language=Python;
}
@header {
import sys
import traceback
from SimpleCalcLexer import SimpleCalcLexer
}
@main {
def main(argv, otherArg=None):
char_stream = ANTLRStringStream(sys.argv[1])
lexer = SimpleCalcLexer(char_stream)
tokens = CommonTokenStream(lexer)
parser = SimpleCalcParser(tokens);
try:
print parser.eval()
except RecognitionException:
traceback.print_stack()
}
eval returns [value]
: add EOF {$value = $add.value}
;
add returns [value]
: m1=mult {$value = $m1.value} ( '+' m2=mult {$value += $m2.value}
| '-' m2=mult {$value -= $m2.value}
)*
;
mult returns [value]
: a1=atom {$value = $a1.value} ( '*' a2=atom {$value *= $a2.value}
| '/' a2=atom {$value /= $a2.value}
)*
;
atom returns [value]
: NUMBER {$value = float($NUMBER.text)}
| '(' add ')' {$value = $add.value}
;
NUMBER : DIGIT+ ('.' DIGIT*)?;
WHITESPACE : ('\t' | ' ' | '\r' | '\n')+ {$channel = HIDDEN;};
fragment DIGIT : '0'..'9' ;
生成词法分析器/解析器并计算表达式:
java -cp antlr-3.1.3.jar org.antlr.Tool SimpleCalc.g
python SimpleCalcParser.py "5 * (8 + 2)"
产生输出:
50.0
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