$ template make_parser()
-# State of the parser automata as stored in the parser stack.
-private class State
- # The internal state number
- readable writable var _state: Int
-
- # The node stored with the state in the stack
- readable writable var _nodes: nullable Object
-
- init(state: Int, nodes: nullable Object)
- do
- _state = state
- _nodes = nodes
- end
-end
-
-class Parser
- super TablesCapable
- # Associated lexer
- var _lexer: Lexer
-
- # Stack of pushed states and productions
- var _stack: Array[State]
-
- # Position in the stack
- var _stack_pos: Int
-
- # Create a new parser based on a given lexer
- init(lexer: Lexer)
- do
- _lexer = lexer
- _stack = new Array[State]
- _stack_pos = -1
- build_reduce_table
- end
-
- # Do a transition in the automata
- private fun go_to(index: Int): Int
- do
- var state = state
- var low = 1
- var high = parser_goto(index, 0) - 1
-
- while low <= high do
- var middle = (low + high) / 2
- var subindex = middle * 2 + 1 # +1 because parser_goto(index, 0) is the length
-
- var goal = parser_goto(index, subindex)
- if state < goal then
- high = middle - 1
- else if state > goal then
- low = middle + 1
- else
- return parser_goto(index, subindex+1)
- end
- end
-
- return parser_goto(index, 2) # Default value
- end
-
- # Push someting in the state stack
- private fun push(numstate: Int, list_node: nullable Object)
- do
- var pos = _stack_pos + 1
- _stack_pos = pos
- if pos < _stack.length then
- var state = _stack[pos]
- state.state = numstate
- state.nodes = list_node
- else
- _stack.push(new State(numstate, list_node))
- end
- end
-
- # The current state
- private fun state: Int
- do
- return _stack[_stack_pos].state
- end
-
- # Pop something from the stack state
- private fun pop: nullable Object
- do
- var res = _stack[_stack_pos].nodes
- _stack_pos = _stack_pos -1
- return res
- end
-
- # Build and return a full AST.
- fun parse: Start
- do
- push(0, null)
-
- var lexer = _lexer
- loop
- var token = lexer.peek
- if token isa PError then
- return new Start(null, token)
- end
-
- var state = self.state
- var index = token.parser_index
- var action_type = parser_action(state, 2)
- var action_value = parser_action(state, 3)
-
- var low = 1
- var high = parser_action(state, 0) - 1
-
- while low <= high do
- var middle = (low + high) / 2
- var subindex = middle * 3 + 1 # +1 because parser_action(state, 0) is the length
-
- var goal = parser_action(state, subindex)
- if index < goal then
- high = middle - 1
- else if index > goal then
- low = middle + 1
- else
- action_type = parser_action(state, subindex+1)
- action_value = parser_action(state, subindex+2)
- break
- end
- end
-
- if action_type == 0 then # SHIFT
- push(action_value, lexer.next)
- else if action_type == 1 then # REDUCE
- _reduce_table[action_value].action(self)
- else if action_type == 2 then # ACCEPT
- var node2 = lexer.next
- assert node2 isa EOF
- var node1 = pop
- assert node1 isa ${/parser/prods/prod/@ename}
- var node = new Start(node1, node2)
- (new ComputeProdLocationVisitor).enter_visit(node)
- return node
- else if action_type == 3 then # ERROR
- var node2 = new PParserError.init_parser_error("Syntax error: unexpected {token}.", token.location, token)
- var node = new Start(null, node2)
- return node
- end
- end
- end
-
- var _reduce_table: Array[ReduceAction]
- private fun build_reduce_table
+redef class Parser
+ redef fun build_reduce_table
do
_reduce_table = new Array[ReduceAction].with_items(
$ foreach {rules/rule}
end
end
-redef class Prod
- # Location on the first token after the start of a production
- # So outside the production for epilon production
- var _first_location: nullable Location
-end
-
-# Find location of production nodes
-# Uses existing token locations to infer location of productions.
-private class ComputeProdLocationVisitor
- super Visitor
- # Currenlty visited productions that need a first token
- var _need_first_prods: Array[Prod] = new Array[Prod]
-
- # Already visited epsilon productions that waits something after them
- var _need_after_epsilons: Array[Prod] = new Array[Prod]
-
- # Location of the last visited token in the current production
- var _last_location: nullable Location = null
-
- redef fun visit(n: ANode)
- do
- if n isa Token then
- var loc = n.location
- _last_location = loc
-
- # Add a first token to productions that need one
- if not _need_first_prods.is_empty then
- for no in _need_first_prods do
- no._first_location = loc
- end
- _need_first_prods.clear
- end
-
- # Find location for already visited epsilon production that need one
- if not _need_after_epsilons.is_empty then
- var loco = new Location(loc.file, loc.line_start, loc.line_start, loc.column_start, loc.column_start)
- for no in _need_after_epsilons do
- no.location = loco
- end
- _need_after_epsilons.clear
- end
- else
- assert n isa Prod
- _need_first_prods.add(n)
-
- n.visit_all(self)
-
- var startl = n._first_location
- if startl != null then
- # Non-epsilon production
- var endl = _last_location
- assert endl != null
-
- n.location = new Location(startl.file, startl.line_start, endl.line_end, startl.column_start, endl.column_end)
-
- if not _need_after_epsilons.is_empty then
- var loc = new Location(endl.file, endl.line_end, endl.line_end, endl.column_end, endl.column_end)
- for no in _need_after_epsilons do
- # Epsilon production that finishes the current non-epsilon production
- no.location = loc
- end
- _need_after_epsilons.clear
- end
- else
- # Epsilon production in the middle or that finishes a parent non-epsilon production
- _need_after_epsilons.add(n)
- end
- end
- end
-
- init do end
-end
-
-# Each reduca action has its own class, this one is the root of the hierarchy.
-private abstract class ReduceAction
- fun action(p: Parser) is abstract
- fun concat(l1, l2 : Array[Object]): Array[Object]
- do
- if l1.is_empty then return l2
- l1.append(l2)
- return l1
- end
- var _goto: Int
- init(g: Int) do _goto = g
-end
-
$ foreach {rules/rule}
private class ReduceAction@index
super ReduceAction
nitlanguage / nit.git / blobdiff