Generating simple AST in ANTLR - antlr

Question

I'm playing a bit around with ANTLR, and wish to create a function like this:
MOVE x y z pitch roll
That produces the following AST:
MOVE
|---x
|---y
|---z
|---pitch
|---roll
So far I've tried without luck, and I keep getting the AST to have the parameters as siblings, rather than children.
Code so far:
C#:
class Program
{
const string CRLF = "\r\n";
static void Main(string[] args)
{
string filename = "Script.txt";
var reader = new StreamReader(filename);
var input = new ANTLRReaderStream(reader);
var lexer = new ScorBotScriptLexer(input);
var tokens = new CommonTokenStream(lexer);
var parser = new ScorBotScriptParser(tokens);
var result = parser.program();
var tree = result.Tree as CommonTree;
Print(tree, "");
Console.Read();
}
static void Print(CommonTree tree, string indent)
{
Console.WriteLine(indent + tree.ToString());
if (tree.Children != null)
{
indent += "\t";
foreach (var child in tree.Children)
{
var childTree = child as CommonTree;
if (childTree.Text != CRLF)
{
Print(childTree, indent);
}
}
}
}
ANTLR:
grammar ScorBotScript;
options
{
language = 'CSharp2';
output = AST;
ASTLabelType = CommonTree;
backtrack = true;
memoize = true;
}
#parser::namespace { RSD.Scripting }
#lexer::namespace { RSD.Scripting }
program
: (robotInstruction CRLF)*
;
robotInstruction
: moveCoordinatesInstruction
;
/**
* MOVE X Y Z PITCH ROLL
*/
moveCoordinatesInstruction
: 'MOVE' x=INT y=INT z=INT pitch=INT roll=INT
;
INT : '-'? ( '0'..'9' )*
;
COMMENT
: '//' ~( CR | LF )* CR? LF { $channel = HIDDEN; }
;
WS
: ( ' ' | TAB | CR | LF ) { $channel = HIDDEN; }
;
ID : ('a'..'z'|'A'..'Z'|'_') ('a'..'z'|'A'..'Z'|'0'..'9'|'_')*
;
STRING
: '"' ( ESC_SEQ | ~('\\'|'"') )* '"'
;
fragment
ESC_SEQ
: '\\' ('b'|'t'|'n'|'f'|'r'|'\"'|'\''|'\\')
;
fragment TAB
: '\t'
;
fragment CR
: '\r'
;
fragment LF
: '\n'
;
CRLF
: (CR ? LF) => CR ? LF
| CR
;
parse
: ID
| INT
| COMMENT
| STRING
| WS
;

Answer 1

I'm a beginner with ANTLR myself, this confused me too.
I think if you want to create a tree from your grammar that has structure, you augment your grammar with hints using the ^ and ! characters. This examples page shows how.
From the linked page:
By default ANTLR creates trees as
"sibling lists".
The grammar must be annotated to with
tree commands to produce a parser that
creates trees in the correct shape
(that is, operators at the root, which
operands as children). A somewhat more
complicated expression parser can be
seen here and downloaded in tar form
here. Note that grammar terminals
which should be at the root of a
sub-tree are annotated with ^.