[antlr-interest] Re: SQL grammar tree construction problem
Joshua Davis
joshua.davis at kiodex.com
Tue Nov 11 16:23:12 PST 2003
Just a quick follow up. The Parser did not build an AST because the
rule that had fired did not specify which token should be the root of
the sub-tree. For example:
fromClause : FROM identifier (AS identifier)?
The AST builder seems to require that one of the tokens be designated
as the root. I changed it to:
fromClause : FROM^ identifier (AS identifier)?
and it worked.
--- In antlr-interest at yahoogroups.com, "Joshua Davis"
<joshua.davis at k...> wrote:
> My example is even simpler. It's *supposed* to generate a node for
> every rule if the buildAST is set to true isn't it? I was under
the
> impression that explicitly creating nodes is not necessary if
> buildAST is enabled.
>
> --- In antlr-interest at yahoogroups.com, Gustav Boström
<i93gusbo at h...>
> wrote:
> > Hi!
> >
> > Thanks for the help!
> >
> > I think I'm trying the same thing as you, but also without luck.
> > I try to do:
> > sql_stmt :
> > sql_data_stmt { #sql_stmt = #([SQL_STMT,"sql_stmt"],
> > #sql_stmt); }
> >
> > , but I never find this node in the tree. The code seems to be
> > generated, but has no effect. Could it be that no root node is
ever
> > created?
> >
> > I also tried this:
> > sql_script :
> > (sql_stmt)? { #sql_script = #
> > ([Token.MIN_USER_TYPE,"sql_script"], #sql_script); } ( SEMICOLON
> > (sql_stmt)? )*
> >
> > "sql_script" is the first rule and now a node is in fact created,
> but
> > it has no children. I thought that all the subsequent nodes would
> be
> > added as children automatically.
> >
> > Qoute from doc:
> > "Setting the return tree is very useful in combination with
normal
> > tree construction because you can have ANTLR do all the work of
> > building a tree and then add an imaginary root node such as:
> >
> > decl : ( TYPE ID )+
> > { #decl = #([DECL,"decl"], #decl); }
> > ;
> > ANTLR allows you to assign to #rule anywhere within an
alternative
> of
> > the rule. ANTLR ensures that references of and assignments to
#rule
> > within an action force the parser's internal AST construction
> > variables into a stable state. After you assign to #rule, the
state
> > of the parser's automatic AST construction variables will be set
as
> > if ANTLR had generated the tree rooted at #rule. For example, any
> > children nodes added after the action will be added to the
children
> > of #rule."
> >
> > This is exactly what I want, but I must be doing something wrong.
> >
> >
> >
> > /Gustav
> >
> >
> >
> > --- In antlr-interest at yahoogroups.com, "Joshua Davis"
> > <joshua.davis at k...> wrote:
> > > ANTLR newbie question:
> > >
> > > I've been having a similar problem I think. I made a very
simple
> > > grammar based on L. V.'s grammar. It seems to be always
> producing
> > > only one root node, with no children. What steps should I take
> to
> > > debug this? I have tried adding actions to the rules, and it
> looks
> > > like the rules are being triggered correctly, but no AST is
> > produced.
> > >
> > > --- In antlr-interest at yahoogroups.com, "lgcraymer" <lgc at m...>
> wrote:
> > > > Gustav--
> > > >
> > > > You cannot make a rule a root--that's what ANTLR is
complaining
> > > about.
> > > > Rules may represent subtrees, so only nodes with token ids
> (TEXT
> > > or
> > > > STRING, for example) can be followed with ^.
> > > >
> > > > --Loring
> > > >
> > > >
> > > > --- In antlr-interest at yahoogroups.com, Gustav Boström
> > > <i93gusbo at h...>
> > > > wrote:
> > > > > Hello!
> > > > >
> > > > > I'm trying to use Lubos Vnuk's (Thanks for doing all the
> work!)
> > > SQL-
> > > > > grammar in order to do some
> > > > > processing on SQL-statments. I would for example like to
find
> > out
> > > > > which columns are affected by a DML-statement and which
> > > parameters
> > > > > correspond to which columns.
> > > > >
> > > > > I'm doing this is in Java , so I've changed the grammar
> > slightly.
> > > > > I've removed the C++ actions or replaced them with Java
> > versions.
> > > > >
> > > > > My thought was to add AST-construction and then navigate
the
> > tree
> > > to
> > > > > find out the stuff I need. This is where I run into
problems.
> > > > > I tried to annotate the rules with ^ to construct my tree,
> but
> > it
> > > > > keeps giving me "unexpected token:^" when I try to dothis
for
> > > > example:
> > > > > sql_stmt :
> > > > > sql_data_stmt^
> > > > > ;
> > > > >
> > > > > I've set the options to buildAST=true;
> > > > > I'm using version 2.7.2.
> > > > >
> > > > > Any ideas on what can be wrong?
> > > > >
> > > > > Cheers,
> > > > >
> > > > > Gustav Boström
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