[antlr-interest] Tree transformation

Arnar Birgisson arnarb at oddi.is
Sun Nov 16 11:54:44 PST 2003


I forgot to mention:
The output of traceTreeParser looks exactly the same for the pair inside
block..endblock and the one outside of it.

Arnar

> -----Original Message-----
> From: Arnar Birgisson [mailto:arnarb at oddi.is] 
> Sent: 16. nóvember 2003 19:52
> To: antlr-interest at yahoogroups.com
> Subject: RE: [antlr-interest] Tree transformation
> 
> 
> Hello again..
> 
> I solved this problem by rewriting the transformation so that 
> it worked
> without the !. However, I keep hitting this wall in other places, and
> now I'm completely stuck. Consider those (simplified) constructs in my
> language
> 
> f -> procedure()
> var x
> body
>   expression1,
>   block
>     x := \incr x,
>     \print [1,2,3]
>   endblock,
>   x := \incr ,
>   \print [1,2,3]
> endbody
> 
> Now.. the expressions "\incr x" and "[1,2,3]" have such trees:
> 
> #([OPERATOR,"incr"] x)
> #([LIST,"["] #([EXPR_LIST] 1 2 3) )
> 
> and I have rules in my tree transformer that changes them to the
> equivalent of the expressions "incr(x)" (function call) and
> "mk_pair(1,mk_pair(2,mk_pair(3,[])))". This transformation works very
> well for the second pair of those expressions.
> 
> Now I want to make a transformation for turning
> 
> BLOCK
>  | 
> EXPR_LIST
>  |
> expr1 - expr2 - ... - exprN
> 
> to
> 
> expr1 - expr2 - ... - exprN.
> 
> For this I have the rule alternative
> 
> |! #(BLOCK list:expr_list)
> 	{
> 		## = list->getFirstChild();
> 	}
> 
> This seems to work except that the transformations inside 
> this instance
> of expr_list don't get executed. Therefore, the transformation of the
> code above is applied only to the second pair of afformentioned
> expressions.
> 
> I'm using exactly the same rule (expr_list) to traverse the list of
> expressions whether they are inside the procedure body, or inside a
> block. I'm stumped!
> 
> If I remove the ! I get two copies of the subtree, one where
> transformations have been applied, and one where they havent...
> 
> Am I doing something terribly wrong or is this unexpected behaviour?
> 
> Arnar
> 
> 
> > -----Original Message-----
> > From: mzukowski at yci.com [mailto:mzukowski at yci.com] 
> > Sent: 14. nóvember 2003 18:39
> > To: antlr-interest at yahoogroups.com
> > Subject: RE: [antlr-interest] Tree transformation
> > 
> > 
> > Hard to tell.  I recommend using -traceParser and following 
> > through the code
> > to see what's happening.
> > 
> > Monty
> > 
> > -----Original Message-----
> > From: Arnar Birgisson [mailto:arnarb at oddi.is] 
> > Sent: Friday, November 14, 2003 7:24 AM
> > To: antlr-interest at yahoogroups.com
> > Subject: [antlr-interest] Tree transformation
> > 
> > Hello..
> > 
> > I'm having some trouble I can't figure out, possibly 
> because I'm doing
> > something stupid.
> > 
> > I have this rule in a tree parser for transforming loops:
> > 
> > loop_stmt
> > 	: #(L_LOOP stmt_list)
> > 	| #(L_WHILE expr stmt_list)
> > 	|! #(L_FOR init:stmt_list test:expr incr:stmt_list
> > body:stmt_list)
> > 		{
> > 			/* this changes "for" loops to "while" loops */
> > 			antlr::RefAST newbody;
> > 			antlr::RefAST lastBodyStmt =
> > body->getFirstChild();
> > 			if (antlr::nullAST == lastBodyStmt) {
> > 				newbody = incr;
> > 			} else {
> > 				while (antlr::nullAST !=
> > lastBodyStmt->getNextSibling())
> > 					lastBodyStmt =
> > lastBodyStmt->getNextSibling();
> > 	
> > lastBodyStmt->setNextSibling(incr->getFirstChild());
> > 				newbody = body;
> > 			}
> > 			antlr::RefAST l = #([L_WHILE,"while"], test,
> > newbody);
> > 			antlr::RefAST lastInitStmt =
> > init->getFirstChild();
> > 			if (antlr::nullAST == lastInitStmt) {
> > 				## = l;
> > 			} else {
> > 				while (antlr::nullAST !=
> > lastInitStmt->getNextSibling())
> > 					lastInitStmt =
> > lastInitStmt->getNextSibling();
> > 				lastInitStmt->setNextSibling(l);
> > 				## = init->getFirstChild();
> > 			}
> > 		}
> > 	;
> > 
> > Now, stmt_list is a simple rule
> > 
> > stmt_list
> > 	: #(STMT_LIST (stmt)*)
> > 	;
> > 
> > and the stmt rule is a big rule, with one alternative being this
> > (note that in my language there is no difference between 
> > statements and
> > expressions):
> > 
> > 	|! #(OPERATOR s1:expr s2:expr)
> > 		{
> > 			/* this changes "x <op> b" to the function call
> > "<op>(x,y)"
> > 			#OPERATOR->setType(ID);
> > 			## = #([OPEN_PAR,"("], ADGERD,
> > #([stmt_list,"params"], s1, s2));
> > 		}
> > 
> > Now, this alternative successfully transforms operator statements to
> > function alls when they are top level statements in functions 
> > (accessed
> > throught stmt_list), but when they're in a for-loop body 
> > (named "body")
> > in the above rule, no transformation takes place, i.e. 
> #(OPERATOR expr
> > expr) is left as is.
> > 
> > I've tried removing the ! in the for-loop rule but that 
> doesn't help..
> > the transformation doesn't take place.
> > 
> > Any ideas?
> > 
> > Arnar
> > 
> > 
> >  
> > 
> > Your use of Yahoo! Groups is subject to 
> > http://docs.yahoo.com/info/terms/ 
> > 
> > 
> >  
> > 
> > Your use of Yahoo! 
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> > 
> > 
> 
> 
>  
> 
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> 
> 


 

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