Velocity - Velocity Specification - AST

Please note that this is currently out of date and will be updated soon.

This is tentatively the AST structure for Velocity.
The structure is as would be described using ANTLR
BNF-style notation. A tree is described by 
#(node node node) where #() represents the tree form. 
The first node is the root of the tree, and following 
nodes are all children.
Visually, #(A B C D E) might look like:
 A
 |
 B-C-D-E
Root nodes must always be a terminal node, denoted by
an all-caps identifier.
Non-root nodes may be either terminal nodes, or sub-rules,
or inlined sub-trees. 
A sub-rule might describe a tree, or simple a node.
block
	:
		#(	BLOCK
				(statement)*
		)
	;
statement
	:
			text
		|	if_statement
		|	foreach_statement
		|	include_statement
		|	set_statement
		|	parse_statement
		|	param_statement
		|	stop_statement
		|	reference
	;
text
	:
		TEXT
	;
//	if/elseif/else chains should be represented solely
//	by <if_statement>. <elseif> is simply an <if_statement>
//	in the false-branch of the preceeding <if_statement>
//	while <else> is simply an <if_statement> where the
//	<expr> evaluates to TRUE always, and no false-branch
//	is provided.
if_statement
	:
		#(	IF
				// The expression to test
				expr
				// True branch
				block
				// False branch
				( block )?
		)
	;
foreach_statement
	:
		#(	FOREACH
				// Value to assign for each iteration
				reference
				// List of objects to iterator
				reference
				// command-block to execute
				( block )?
		)
	;
set_statement
	:
		#(	SET
				// Variable to set
				reference
				// Value to assign
				expr
	;
parse_statement
	:
		#(	PARSE
				STRING_LITERAL
		)
	;
include_statement
	:
		#(	INCLUDE
				STRING_LITERAL
		)
	;
stop_statement
	:
		STOP
	;
reference
	:
		#(	REFERENCE
				postfix
	;
postfix
	:
		method_call
		|
		member
		|
		identifier
	;
member
	:
		#(	DOT
				identifier
				(	primary
				|	method_call
				)	
	;
primary
	:
		IDENTIFIER
	;
method_call
		#(	CALL
				postfix
				// The argument list
				( expr ) *
		)
	;