[antlr-interest] Get Values after parse

[Harald M. Müller]

Usually, you would just add actions to the grammar which store the relevant
values somewhere else - typically in the parser object itself:
 
grammar SomeSQL;
 
@members {
    public List<String> columnNames = new ArrayList<String>();
    public String whereClause;
    // instead of public, write accessors in real-life code ...
}
 
sql : selectClause fromClause whereClause?
     ;
 
selectClause 
     : 'select' columnList
     ;
 
columnList 
     : (ID '.')? '*'        { columnNames.Add(...???...); }
     | c1=column        { columnNames.Add($c1.text); }
       ( ','
         c2=column        { columnNames.Add($c2.text); }
       )*
     ;
 
etc.
 
In your main code, after running
 
     SomeSQLParser p = new SomeSQLParser(...);
     p.sql();
 
you can then get all the information from your SomeSQLParser object:
 
     for (String columnName : p.columnNames) { ... }
     ...o.whereClause...
 
Instead of using the parser class, you can also pass some "storage/context"
object as a parameter to the parser's constructor and have the actions
record their findings in that context (in compiler talk, this would be a
"symbol table").
 
Regards
Harald
 


  _____  

From: antlr-interest-bounces at antlr.org [mailt
o:antlr-interest-bounces at antlr.org] On Behalf Of Cory Isaacson
Sent: Sunday, December 30, 2007 2:56 AM
To: antlr-interest at antlr.org
Subject: [antlr-interest] Get Values after parse



I am new to ANTLR, and have a simple question. I need to parse a simple SQL
SELECT statement, and can see how to create the grammar for the lexer and
parser. I need to then get specific values from the SELECT statement, such
as table name(s), column name(s), the WHERE clause, etc.

 

To actually get the values, do I need to output an AST tree? If so, what is
the simplest way to access specific node/values? 

 

If you can suggest examples to look at and/or the best API to use that would
be great.

 

Thanks in advance for any assistance.

 

Cory

 

 

 

 

 

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