[antlr-interest] RE: Treebuilding ....

[mzukowski at yci.com]

OK, now I kinda see the problem.  Thing is, you didn't post your tree parser
rules so I can't tell why you are having problems in your tree parser.  For
the first example, is "END" a statement that statement_list can match?

OK, now, in this rule you turned tree building off and you are creating a
root called stlist with no children because #statement_list is empty since
you turned off tree building, just what I would expect to happen.  You
almost got the idiom right, just turn tree building back on for the rule.

statement_list! 
        : ( (statement_line (EOL!)+ )+ ) 
        { #statement_list = #(#[STLIST,"stlist"], #statement_list); } 
        ; 

Make it 
statement_list 
        : ( (statement_line (EOL!)+ )+ ) 
        { #statement_list = #(#[STLIST,"stlist"], #statement_list); } 
        ; 

By the way there is a shorthand for #current_rule, which is ## 

statement_list
        : ( (statement_line (EOL!)+ )+ ) 
        { ## = #(#[STLIST,"stlist"], ##); } 
        ; 
Monty

-----Original Message-----
From: Anthony Youngman [mailto:Anthony.Youngman at ECA-International.com]
Sent: Friday, April 04, 2003 7:32 AM
To: 'antlr-interest at yahoogroups.com'
Subject: [antlr-interest] RE: Treebuilding ....


Carrying on from my last problem... now I've got rid of the
non-determinism... 
If my parser contains the definition: 
        statement_line : (statement ( SEMI! statement)* ) ; 
        statement_list : ( (statement_line (EOL!)+ )+ ) ; 
I seem to get the tree I expect namely 
        ( PROGRAM SHELL (LOOP (PRINT...) (INPUT ...) (PRINT ...)  ...)
(PRINT ...) END ) null 
when I print out the tree using 
        System.out.println( "printing AST"); 
        AST result = parser.getAST(); 
        System.out.println(result.toStringList()); 
BUT the treeparser chokes on it. It's expecting "PROGRAM" ID statement_list
"END". It seems to me it's expecting a single "statement_list", and when fed
the expanded list as above it chokes because it gets a LOOP. So I changed
the definition of statement_list to
statement_list! 
        : ( (statement_line (EOL!)+ )+ ) 
        { #statement_list = #(#[STLIST,"stlist"], #statement_list); } 
        ; 
which now gives me 
        ( PROGRAM SHELL stlist END ) null 
when I print the tree. The treeparser chokes on this, because it seems my
statement_list has become a root with no sibs or children or whatever - my
loop, print etc have got lost :-( Apologies if this seems simple - I seem to
have been asking question after question on the list, but I've been tearing
my hair out of the syntax of "statement_list!". Is it right? And if so, why
doesn't "toStringList()" traverse it?
Cheers, 
Wol 


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