[antlr-interest] Help with a tree grammar: losing a list of statements

[Pauba, Kevin L]

Sorry to respond to my own post but I've made some (limited) progress.

I changed the rewriting tree grammar rule from:

        |       ^(KW_while ^(EXPR l=string condition=string r=string) ^(SLIST s+=statement+))
                -> template(lhs={$l.text}, operator={$condition.text}, rhs={$r.text}, stats={$s}) << ... >>

to:

        |       ^(KW_while ^(EXPR l=string condition=string r=string) ^(SLIST s+=statement+))
                -> template(lhs={$l.text}, operator={$condition.text}, rhs={$r.text}, stats={$text}) << ... >>

and now get more substituted for <stats> than I expected:

L:
        ; while $99 > 0
        test $99 > 0 L_END:
        while $99 > 0
                LET $99 - 1
                LET $98 + 1
        endwhile

        goto L:
L_END:

I don't want the "while $99 > 0" or "endwhile" in there, just the text of the tokens for the statements in SLIST.

Reading TDAR a little more, I discovered (again) "Deriving imaginary Nodes from Real Tokens" (pg 175) and modified the parser grammar from:

        |       KW_while l=string condition=string r=string statement+ KW_endwhile
                -> ^(KW_while ^(EXPR $l $condition $r) ^(SLIST statement+))

to:

        |       KW_while l=string condition=string r=string statement+ KW_endwhile
                -> ^(KW_while ^(EXPR $l $condition $r) ^(SLIST[$l,"statements"] statement+))

but I get the following error:

error(117): JCC.g:0:0: missing attribute access on rule scope: l

 (that l is a lower case L).

I welcome any hints or pointers to TDAR sections for a solution.

Thanks!

From: antlr-interest-bounces at antlr.org [mailto:antlr-interest-bounces at antlr.org] On Behalf Of Pauba, Kevin L
Sent: Monday, November 30, 2009 11:31 AM
To: antlr-interest
Subject: [antlr-interest] Help with a tree grammar: losing a list of statements

I have a parser and tree grammar written to add better flow control constructs to an assembly language-like DSL.

Here's the parser grammar rule of interest:

        |       KW_while l=string condition=string r=string statement+ KW_endwhile
                -> ^(KW_while ^(EXPR $l $condition $r) ^(SLIST statement+))

In ANTLRWorks it shows what I expect for an AST using the following text:

while $99 > 0
                let $99 - 1
                let $98 + 1
endwhile

The expected AST includes a tree with a root of KW_while and two children (the EXPR and the SLIST (the list of two statement trees).  I hope that makes sense.

I have a tree-walking grammar that uses "output=template" and "rewrite = true" with the following rule:

        |       ^(KW_while ^(EXPR l=string condition=string r=string) ^(SLIST s+=statement+))
                -> template(lhs={$l.text}, operator={$condition.text}, rhs={$r.text}, stats={$s})
                <<
L:
        ; while <lhs> <operator> <rhs>
        test <lhs> <operator> <rhs> L_END:
        <stats>
        goto L:
L_END:
                >>

I'm doing something wrong as the "<stats>" ends up being null and I get the following output:

L:
        ; while $99 > 0
        test $99 > 0 L_END:
        goto L:
L_END:

What is wrong with my rewrite grammar?

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