$ // This file is part of NIT ( http://www.nitlanguage.org ).
$ //
$ // Copyright 2008 Jean Privat <jean@pryen.org>
$ // Based on algorithms developped for ( http://www.sablecc.org/ ).
$ //
$ // 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.

$ template make_abs_nodes()
# Root of the AST hierarchy
abstract class PNode
	readable var _location: nullable Location
end

# Ancestor of all tokens
abstract class Token
special PNode
end

# Ancestor of all productions
abstract class Prod
special PNode
	fun location=(loc: nullable Location) do _location = loc
end
$ end template

$ template make_nodes()
redef class PNode
	# Parent of the node in the AST
	readable writable var _parent: nullable PNode

	# Remove a child from the AST
	fun remove_child(child: PNode)
	do
		replace_child(child, null)
	end

	# Replace a child with an other node in the AST
	fun replace_child(old_child: PNode, new_child: nullable PNode) is abstract

	# Replace itself with an other node in the AST
	fun replace_with(node: PNode)
	do
		if (_parent != null) then
			_parent.replace_child(self, node)
		end
	end

	# Visit all nodes in order.
	# Thus, call "v.visit(e)" for each node e
	fun visit_all(v: Visitor) is abstract

	# Visit all nodes in reverse order.
	# Thus, call "v.visit(e)" for each node e starting from the last child
	fun visit_all_reverse(v: Visitor) is abstract
end

redef class Token
	redef fun visit_all(v: Visitor) do end
	redef fun visit_all_reverse(v: Visitor) do end
	redef fun replace_child(old_child: PNode, new_child: nullable PNode) do end
end

redef class Prod
	redef fun replace_with(n: PNode)
        do
                super
                assert n isa Prod
                n.location = location
        end
end

# Abstract standard visitor
class Visitor
	# What the visitor do when a node is visited
        # Concrete visitors should redefine this method.
        protected fun visit(e: nullable PNode) is abstract

        # Ask the visitor to visit a given node.
        # Usually automatically called by visit_all* methods.
	# This methos should not be redefined
        fun enter_visit(e: nullable PNode)
	do
		var old = _current_node
		_current_node = e
		visit(e)
		_current_node = old
	end

	# The current visited node
	readable var _current_node: nullable PNode = null
end

$ end template