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require "lrama/grammar/auxiliary"
require "lrama/grammar/code"
require "lrama/grammar/error_token"
require "lrama/grammar/precedence"
require "lrama/grammar/printer"
require "lrama/grammar/reference"
require "lrama/grammar/rule"
require "lrama/grammar/symbol"
require "lrama/grammar/union"
require "lrama/lexer"
require "lrama/type"
module Lrama
Token = Lrama::Lexer::Token
# Grammar is the result of parsing an input grammar file
class Grammar
attr_reader :eof_symbol, :error_symbol, :undef_symbol, :accept_symbol, :aux
attr_accessor :union, :expect,
:printers, :error_tokens,
:lex_param, :parse_param, :initial_action,
:symbols, :types,
:rules, :_rules,
:sym_to_rules
def initialize
@printers = []
@error_tokens = []
@symbols = []
@types = []
@_rules = []
@rules = []
@sym_to_rules = {}
@empty_symbol = nil
@eof_symbol = nil
@error_symbol = nil
@undef_symbol = nil
@accept_symbol = nil
@aux = Auxiliary.new
append_special_symbols
end
def add_printer(ident_or_tags:, code:, lineno:)
@printers << Printer.new(ident_or_tags: ident_or_tags, code: code, lineno: lineno)
end
def add_error_token(ident_or_tags:, code:, lineno:)
@error_tokens << ErrorToken.new(ident_or_tags: ident_or_tags, code: code, lineno: lineno)
end
def add_term(id:, alias_name: nil, tag: nil, token_id: nil, replace: false)
if token_id && (sym = @symbols.find {|s| s.token_id == token_id })
if replace
sym.id = id
sym.alias_name = alias_name
sym.tag = tag
end
return sym
end
if sym = @symbols.find {|s| s.id == id }
return sym
end
sym = Symbol.new(
id: id, alias_name: alias_name, number: nil, tag: tag,
term: true, token_id: token_id, nullable: false
)
@symbols << sym
@terms = nil
return sym
end
def add_nterm(id:, alias_name: nil, tag: nil)
return if @symbols.find {|s| s.id == id }
sym = Symbol.new(
id: id, alias_name: alias_name, number: nil, tag: tag,
term: false, token_id: nil, nullable: nil,
)
@symbols << sym
@nterms = nil
return sym
end
def add_type(id:, tag:)
@types << Type.new(id: id, tag: tag)
end
def add_nonassoc(sym, precedence)
set_precedence(sym, Precedence.new(type: :nonassoc, precedence: precedence))
end
def add_left(sym, precedence)
set_precedence(sym, Precedence.new(type: :left, precedence: precedence))
end
def add_right(sym, precedence)
set_precedence(sym, Precedence.new(type: :right, precedence: precedence))
end
def add_precedence(sym, precedence)
set_precedence(sym, Precedence.new(type: :precedence, precedence: precedence))
end
def set_precedence(sym, precedence)
raise "" if sym.nterm?
sym.precedence = precedence
end
def set_union(code, lineno)
@union = Union.new(code: code, lineno: lineno)
end
def add_rule(lhs:, rhs:, lineno:)
@_rules << [lhs, rhs, lineno]
end
def build_references(token_code)
token_code.references.map! do |type, value, tag, first_column, last_column|
Reference.new(type: type, value: value, ex_tag: tag, first_column: first_column, last_column: last_column)
end
token_code
end
def build_code(type, token_code)
build_references(token_code)
Code.new(type: type, token_code: token_code)
end
def prologue_first_lineno=(prologue_first_lineno)
@aux.prologue_first_lineno = prologue_first_lineno
end
def prologue=(prologue)
@aux.prologue = prologue
end
def epilogue_first_lineno=(epilogue_first_lineno)
@aux.epilogue_first_lineno = epilogue_first_lineno
end
def epilogue=(epilogue)
@aux.epilogue = epilogue
end
def prepare
normalize_rules
collect_symbols
replace_token_with_symbol
fill_symbol_number
fill_default_precedence
fill_sym_to_rules
fill_nterm_type
fill_symbol_printer
fill_symbol_error_token
@symbols.sort_by!(&:number)
end
# TODO: More validation methods
def validate!
validate_symbol_number_uniqueness!
validate_no_declared_type_reference!
end
def compute_nullable
@rules.each do |rule|
case
when rule.rhs.empty?
rule.nullable = true
when rule.rhs.any?(&:term)
rule.nullable = false
else
# noop
end
end
while true do
rs = @rules.select {|e| e.nullable.nil? }
nts = nterms.select {|e| e.nullable.nil? }
rule_count_1 = rs.count
nterm_count_1 = nts.count
rs.each do |rule|
if rule.rhs.all?(&:nullable)
rule.nullable = true
end
end
nts.each do |nterm|
find_rules_by_symbol!(nterm).each do |rule|
if rule.nullable
nterm.nullable = true
end
end
end
rule_count_2 = @rules.count {|e| e.nullable.nil? }
nterm_count_2 = nterms.count {|e| e.nullable.nil? }
if (rule_count_1 == rule_count_2) && (nterm_count_1 == nterm_count_2)
break
end
end
rules.select {|r| r.nullable.nil? }.each do |rule|
rule.nullable = false
end
nterms.select {|r| r.nullable.nil? }.each do |nterm|
nterm.nullable = false
end
end
def compute_first_set
terms.each do |term|
term.first_set = Set.new([term]).freeze
term.first_set_bitmap = Lrama::Bitmap.from_array([term.number])
end
nterms.each do |nterm|
nterm.first_set = Set.new([]).freeze
nterm.first_set_bitmap = Lrama::Bitmap.from_array([])
end
while true do
changed = false
@rules.each do |rule|
rule.rhs.each do |r|
if rule.lhs.first_set_bitmap | r.first_set_bitmap != rule.lhs.first_set_bitmap
changed = true
rule.lhs.first_set_bitmap = rule.lhs.first_set_bitmap | r.first_set_bitmap
end
break unless r.nullable
end
end
break unless changed
end
nterms.each do |nterm|
nterm.first_set = Lrama::Bitmap.to_array(nterm.first_set_bitmap).map do |number|
find_symbol_by_number!(number)
end.to_set
end
end
def find_symbol_by_s_value(s_value)
@symbols.find do |sym|
sym.id.s_value == s_value
end
end
def find_symbol_by_s_value!(s_value)
find_symbol_by_s_value(s_value) || (raise "Symbol not found: #{s_value}")
end
def find_symbol_by_id(id)
@symbols.find do |sym|
# TODO: validate uniqueness of Token#s_value and Symbol#alias_name
sym.id == id || sym.alias_name == id.s_value
end
end
def find_symbol_by_id!(id)
find_symbol_by_id(id) || (raise "Symbol not found: #{id}")
end
def find_symbol_by_number!(number)
sym = @symbols[number]
raise "Symbol not found: #{number}" unless sym
raise "[BUG] Symbol number mismatch. #{number}, #{sym}" if sym.number != number
sym
end
def find_rules_by_symbol!(sym)
find_rules_by_symbol(sym) || (raise "Rules for #{sym} not found")
end
def find_rules_by_symbol(sym)
@sym_to_rules[sym.number]
end
def terms_count
terms.count
end
def terms
@terms ||= @symbols.select(&:term?)
end
def nterms_count
nterms.count
end
def nterms
@nterms ||= @symbols.select(&:nterm?)
end
private
def find_nterm_by_id!(id)
nterms.find do |nterm|
nterm.id == id
end || (raise "Nterm not found: #{id}")
end
def append_special_symbols
# YYEMPTY (token_id: -2, number: -2) is added when a template is evaluated
# term = add_term(id: Token.new(Token::Ident, "YYEMPTY"), token_id: -2)
# term.number = -2
# @empty_symbol = term
# YYEOF
term = add_term(id: Token.new(type: Token::Ident, s_value: "YYEOF"), alias_name: "\"end of file\"", token_id: 0)
term.number = 0
term.eof_symbol = true
@eof_symbol = term
# YYerror
term = add_term(id: Token.new(type: Token::Ident, s_value: "YYerror"), alias_name: "error")
term.number = 1
term.error_symbol = true
@error_symbol = term
# YYUNDEF
term = add_term(id: Token.new(type: Token::Ident, s_value: "YYUNDEF"), alias_name: "\"invalid token\"")
term.number = 2
term.undef_symbol = true
@undef_symbol = term
# $accept
term = add_nterm(id: Token.new(type: Token::Ident, s_value: "$accept"))
term.accept_symbol = true
@accept_symbol = term
end
# 1. Add $accept rule to the top of rules
# 2. Extract precedence and last action
# 3. Extract action in the middle of RHS into new Empty rule
# 4. Append id and extract action then create Rule
#
# Bison 3.8.2 uses different orders for symbol number and rule number
# when a rule has actions in the middle of a rule.
#
# For example,
#
# `program: $@1 top_compstmt`
#
# Rules are ordered like below,
#
# 1 $@1: ε
# 2 program: $@1 top_compstmt
#
# Symbols are ordered like below,
#
# 164 program
# 165 $@1
#
def normalize_rules
# 1. Add $accept rule to the top of rules
accept = find_symbol_by_s_value!("$accept")
eof = find_symbol_by_number!(0)
lineno = @_rules.first ? @_rules.first[2] : 0
@rules << Rule.new(id: @rules.count, lhs: accept, rhs: [@_rules.first[0], eof], code: nil, lineno: lineno)
extracted_action_number = 1 # @n as nterm
@_rules.each do |lhs, rhs, lineno|
a = []
rhs1 = []
code = nil
precedence_sym = nil
# 2. Extract precedence and last action
rhs.reverse.each do |r|
case
when r.is_a?(Symbol) # precedence_sym
precedence_sym = r
when (r.type == Token::User_code) && precedence_sym.nil? && code.nil? && rhs1.empty?
code = r
else
rhs1 << r
end
end
rhs1.reverse!
# Bison n'th component is 1-origin
(rhs1 + [code]).compact.each.with_index(1) do |token, i|
if token.type == Token::User_code
token.references.each do |ref|
# Need to keep position_in_rhs for actions in the middle of RHS
ref.position_in_rhs = i - 1
next if ref.type == :at
# $$, $n, @$, @n can be used in any actions
if ref.value == "$"
# TODO: Should be postponed after middle actions are extracted?
ref.referring_symbol = lhs
elsif ref.value.is_a?(Integer)
raise "Can not refer following component. #{ref.value} >= #{i}. #{token}" if ref.value >= i
rhs1[ref.value - 1].referred = true
ref.referring_symbol = rhs1[ref.value - 1]
elsif ref.value.is_a?(String)
target_tokens = ([lhs] + rhs1 + [code]).compact.first(i)
referring_symbol_candidate = target_tokens.filter {|token| token.referred_by?(ref.value) }
raise "Referring symbol `#{ref.value}` is duplicated. #{token}" if referring_symbol_candidate.size >= 2
raise "Referring symbol `#{ref.value}` is not found. #{token}" if referring_symbol_candidate.count == 0
referring_symbol = referring_symbol_candidate.first
referring_symbol.referred = true
ref.referring_symbol = referring_symbol
end
end
end
end
rhs2 = rhs1.map do |token|
if token.type == Token::User_code
prefix = token.referred ? "@" : "$@"
new_token = Token.new(type: Token::Ident, s_value: prefix + extracted_action_number.to_s)
extracted_action_number += 1
a << [new_token, token]
new_token
else
token
end
end
# Extract actions in the middle of RHS
# into new rules.
a.each do |new_token, code|
@rules << Rule.new(id: @rules.count, lhs: new_token, rhs: [], code: Code.new(type: :user_code, token_code: code), lineno: code.line)
end
c = code ? Code.new(type: :user_code, token_code: code) : nil
@rules << Rule.new(id: @rules.count, lhs: lhs, rhs: rhs2, code: c, precedence_sym: precedence_sym, lineno: lineno)
add_nterm(id: lhs)
a.each do |new_token, _|
add_nterm(id: new_token)
end
end
end
# Collect symbols from rules
def collect_symbols
@rules.flat_map(&:rhs).each do |s|
case s
when Token
if s.type == Token::Char
add_term(id: s)
end
when Symbol
# skip
else
raise "Unknown class: #{s}"
end
end
end
# Fill #number and #token_id
def fill_symbol_number
# TODO: why start from 256
token_id = 256
# YYEMPTY = -2
# YYEOF = 0
# YYerror = 1
# YYUNDEF = 2
number = 3
nterm_token_id = 0
used_numbers = {}
@symbols.map(&:number).each do |n|
used_numbers[n] = true
end
(@symbols.select(&:term?) + @symbols.select(&:nterm?)).each do |sym|
while used_numbers[number] do
number += 1
end
if sym.number.nil?
sym.number = number
number += 1
end
# If id is Token::Char, it uses ASCII code
if sym.term? && sym.token_id.nil?
if sym.id.type == Token::Char
# Ignore ' on the both sides
case sym.id.s_value[1..-2]
when "\\b"
sym.token_id = 8
when "\\f"
sym.token_id = 12
when "\\n"
sym.token_id = 10
when "\\r"
sym.token_id = 13
when "\\t"
sym.token_id = 9
when "\\v"
sym.token_id = 11
when "\""
sym.token_id = 34
when "'"
sym.token_id = 39
when "\\\\"
sym.token_id = 92
when /\A\\(\d+)\z/
sym.token_id = Integer($1, 8)
when /\A(.)\z/
sym.token_id = $1.bytes.first
else
raise "Unknown Char s_value #{sym}"
end
else
sym.token_id = token_id
token_id += 1
end
end
if sym.nterm? && sym.token_id.nil?
sym.token_id = nterm_token_id
nterm_token_id += 1
end
end
end
def replace_token_with_symbol
@rules.each do |rule|
rule.lhs = token_to_symbol(rule.lhs)
rule.rhs.map! do |t|
token_to_symbol(t)
end
if rule.code
rule.code.references.each do |ref|
next if ref.type == :at
if ref.referring_symbol.type != Token::User_code
ref.referring_symbol = token_to_symbol(ref.referring_symbol)
end
end
end
end
end
def token_to_symbol(token)
case token
when Token
find_symbol_by_id!(token)
when Symbol
token
else
raise "Unknown class: #{token}"
end
end
# Rule inherits precedence from the last term in RHS.
#
# https://www.gnu.org/software/bison/manual/html_node/How-Precedence.html
def fill_default_precedence
@rules.each do |rule|
# Explicitly specified precedence has the highest priority
next if rule.precedence_sym
precedence_sym = nil
rule.rhs.each do |sym|
precedence_sym = sym if sym.term?
end
rule.precedence_sym = precedence_sym
end
end
def fill_sym_to_rules
@rules.each do |rule|
key = rule.lhs.number
@sym_to_rules[key] ||= []
@sym_to_rules[key] << rule
end
end
# Fill nterm's tag defined by %type decl
def fill_nterm_type
@types.each do |type|
nterm = find_nterm_by_id!(type.id)
nterm.tag = type.tag
end
end
def fill_symbol_printer
@symbols.each do |sym|
@printers.each do |printer|
printer.ident_or_tags.each do |ident_or_tag|
case ident_or_tag.type
when Token::Ident
sym.printer = printer if sym.id == ident_or_tag
when Token::Tag
sym.printer = printer if sym.tag == ident_or_tag
else
raise "Unknown token type. #{printer}"
end
end
end
end
end
def fill_symbol_error_token
@symbols.each do |sym|
@error_tokens.each do |error_token|
error_token.ident_or_tags.each do |ident_or_tag|
case ident_or_tag.type
when Token::Ident
sym.error_token = error_token if sym.id == ident_or_tag
when Token::Tag
sym.error_token = error_token if sym.tag == ident_or_tag
else
raise "Unknown token type. #{error_token}"
end
end
end
end
end
def validate_symbol_number_uniqueness!
invalid = @symbols.group_by(&:number).select do |number, syms|
syms.count > 1
end
return if invalid.empty?
raise "Symbol number is duplicated. #{invalid}"
end
def validate_no_declared_type_reference!
errors = []
rules.each do |rule|
next unless rule.code
rule.code.references.select do |ref|
ref.type == :dollar && !ref.tag
end.each do |ref|
errors << "$#{ref.value} of '#{rule.lhs.id.s_value}' has no declared type"
end
end
return if errors.empty?
raise errors.join("\n")
end
end
end
|