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<?xml version="1.0"?>
<!--
Copyright 2000-2004 The Apache Software Foundation
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
-->
<document>
<properties>
<title>Velocity Specification - AST</title>
<author email="jon@latchkey.com">Velocity Documentation Team</author>
</properties>
<body>
<section name="Velocity Specification - AST">
<p>
Please note that this is currently out of date and will be updated soon.
</p>
<source><![CDATA[
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 ) *
)
;
]]></source>
</section>
</body>
</document>
|
