用于和/或逻辑的Antlr解析器-如何在逻辑运算符之间获取表达式?

问题描述

我正在使用ANTLR创建和/或解析器+评估器.表达式的格式如下:

I am using ANTLR to create an and/or parser+evaluator. Expressions will have the format like:

• x eq 1 && y eq 10
• (x lt 10 && x gt 1) OR x eq -1

• x eq 1 && y eq 10
• (x lt 10 && x gt 1) OR x eq -1

我正在阅读有关ANTLR中的逻辑表达式的文章寻找建议在项目上.解析逻辑表达式，我发现那里发布的语法是一个好的开始:

I was reading this post on logic expressions in ANTLR Looking for advice on project. Parsing logical expression and I found the grammar posted there a good start:

grammar Logic;

parse
  :  expression EOF
  ;

expression
  :  implication
  ;

implication
  :  or ('->' or)*
  ;

or
  :  and ('&&' and)*
  ;

and
  :  not ('||' not)*
  ;

not
  :  '~' atom
  |  atom
  ;

atom
  :  ID
  |  '(' expression ')'
  ;

ID    : ('a'..'z' | 'A'..'Z')+;
Space : (' ' | '\t' | '\r' | '\n')+ {$channel=HIDDEN;};

但是，虽然从解析器中获取一棵树可用于变量只是一个字符的表达式(即"(A || B) AND C"，但我很难适应这种情况(在示例"x eq 1 && y eq 10"中，希望有一个"AND"父级和两个孩子"x eq 1"和"y eq 10"，请参见下面的测试用例.

However, while getting a tree from the parser works for expressions where the variables are just one character (ie, "(A || B) AND C", I am having a hard time adapting this to my case (in the example "x eq 1 && y eq 10" I'd expect one "AND" parent and two children, "x eq 1" and "y eq 10", see the test case below).

@Test
public void simpleAndEvaluation() throws RecognitionException{
    String src = "1 eq 1 && B";

    LogicLexer lexer = new LogicLexer(new ANTLRStringStream(src));
    LogicParser parser = new LogicParser(new CommonTokenStream(lexer));


    CommonTree tree = (CommonTree)parser.parse().getTree();

    assertEquals("&&",tree.getText());
    assertEquals("1 eq 1",tree.getChild(0).getText());
    assertEquals("a neq a",tree.getChild(1).getText());
}

我相信这与"ID"有关.正确的语法是什么?

I believe this is related with the "ID". What would the correct syntax be?

推荐答案

对于那些感兴趣的人，我在语法文件中做了一些改进(请参见下面的内容)

For those interested, I made some improvements in my grammar file (see bellow)

当前限制:

• 仅适用于&&/||，而不适用于AND/OR(问题不大)

• only works with &&/||, not AND/OR (not very problematic)

在括号和&&/||之间不能有空格. (我通过在提供词法分析器之前在源字符串中用("替换为)"和)"替换为)来解决此问题)

you can't have spaces between the parenthesis and the &&/|| (I solve that by replacing " (" with ")" and ") " with ")" in the source String before feeding the lexer)

语法逻辑；

options {
  output = AST;
}

tokens {
  AND = '&&';
  OR  = '||';
  NOT = '~';
}

// parser/production rules start with a lower case letter
parse
  :  expression EOF!    // omit the EOF token
  ;

expression
  :  or
  ;

or
  :  and (OR^ and)*    // make `||` the root
  ;

and
  :  not (AND^ not)*      // make `&&` the root
  ;

not
  :  NOT^ atom    // make `~` the root
  |  atom
  ;

atom
  :  ID
  |  '('! expression ')'!    // omit both `(` and `)`
  ;

// lexer/terminal rules start with an upper case letter
ID
  :
    (
    'a'..'z'
    | 'A'..'Z'
    | '0'..'9' | ' '
    | SYMBOL
  )+ 
  ;

SYMBOL
  :
    ('+'|'-'|'*'|'/'|'_')
 ;

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