[antlr-interest] Re: Line number information for AST

[antlrlist]

<hiteshk25 at y...> wrote:
> 
> Hi,
> 
>      How to get line number, which says token of AST
> node belong to that line.
> 
> with regards,
> Hitesh.

Hi Hitesh!

The key is this: in ANTLR, AST nodes are completely different from 
tokens. ASTs are (normally) instances of antlr.CommonAST, while 
tokens are (normally) instances of antlr.CommonToken. These are 
completely different classes (no inheritance neither composition 
between them). They just "look" similar, because both have a "type" 
attribute and a "text" attribute. CommonType can even be initialized 
with a Token, but don't let this dissapoint you: only type and text 
are copied. This is where similarities end: AST nodes don't have 
file line or columns!

Putting aside the design reasons for this implementation, let me 
reformulate your question:
    How do I *add* line and column to the AST nodes?

This is easy: you can subclass antlr.CommonAST and add your own line 
and column attributes. Then override the initialize() methods so 
they copy line and column from the tokens, and add get and set 
methods.

Finally, you'll have to make your parser use your new AST node class 
instead of antlr.CommonAST... but I'll let you guess how to do it :)

...

I was joking :D! Use options ASTLabelType 
(http://www.antlr.org/doc/options.html#_bb13) and
Parser.setASTNodeType 
(http://www.antlr.org/javadoc/antlr/Parser.html#setASTNodeType
(java.lang.String))

However, if you want to make your life easier, you can use my lib, 
antlraux (http://antlraux.sf.net). It has a class, LexInfoAST 
(http://antlraux.sourceforge.net/javadoc/antlraux/util/LexInfoAST.htm
l) that will match your needs perfectly (it even includes filename 
O_O)

Cya!




 

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