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module Lrama
class Grammar
class RuleBuilder
attr_accessor :lhs, :line
attr_reader :lhs_tag, :rhs, :user_code, :precedence_sym
def initialize(rule_counter, midrule_action_counter, position_in_original_rule_rhs = nil, lhs_tag: nil, skip_preprocess_references: false)
@rule_counter = rule_counter
@midrule_action_counter = midrule_action_counter
@position_in_original_rule_rhs = position_in_original_rule_rhs
@skip_preprocess_references = skip_preprocess_references
@lhs = nil
@lhs_tag = lhs_tag
@rhs = []
@user_code = nil
@precedence_sym = nil
@line = nil
@rules = []
@rule_builders_for_parameterizing_rules = []
@rule_builders_for_derived_rules = []
@rule_builders_for_inline_rules = []
@parameterizing_rules = []
@inline_rules = []
@midrule_action_rules = []
end
def add_rhs(rhs)
if !@line
@line = rhs.line
end
flush_user_code
@rhs << rhs
end
def user_code=(user_code)
if !@line
@line = user_code&.line
end
flush_user_code
@user_code = user_code
end
def precedence_sym=(precedence_sym)
flush_user_code
@precedence_sym = precedence_sym
end
def complete_input
freeze_rhs
end
def setup_rules(parameterizing_rule_resolver)
preprocess_references unless @skip_preprocess_references
if rhs.any? { |token| parameterizing_rule_resolver.find_inline(token) }
resolve_inline(parameterizing_rule_resolver)
else
process_rhs(parameterizing_rule_resolver)
end
build_rules
end
def rules
@parameterizing_rules + @inline_rules + @midrule_action_rules + @rules
end
private
def freeze_rhs
@rhs.freeze
end
def preprocess_references
numberize_references
end
def build_rules
tokens = @replaced_rhs
if tokens
rule = Rule.new(
id: @rule_counter.increment, _lhs: lhs, _rhs: tokens, lhs_tag: lhs_tag, token_code: user_code,
position_in_original_rule_rhs: @position_in_original_rule_rhs, precedence_sym: precedence_sym, lineno: line
)
@rules = [rule]
@parameterizing_rules = @rule_builders_for_parameterizing_rules.map do |rule_builder|
rule_builder.rules
end.flatten
@midrule_action_rules = @rule_builders_for_derived_rules.map do |rule_builder|
rule_builder.rules
end.flatten
@midrule_action_rules.each do |r|
r.original_rule = rule
end
else
@inline_rules = @rule_builders_for_inline_rules.map do |rule_builder|
rule_builder.rules
end.flatten
end
end
# rhs is a mixture of variety type of tokens like `Ident`, `InstantiateRule`, `UserCode` and so on.
# `#process_rhs` replaces some kind of tokens to `Ident` so that all `@replaced_rhs` are `Ident` or `Char`.
def process_rhs(parameterizing_rule_resolver)
return if @replaced_rhs
@replaced_rhs = []
rhs.each_with_index do |token, i|
case token
when Lrama::Lexer::Token::Char
@replaced_rhs << token
when Lrama::Lexer::Token::Ident
@replaced_rhs << token
when Lrama::Lexer::Token::InstantiateRule
parameterizing_rule = parameterizing_rule_resolver.find_rule(token)
raise "Unexpected token. #{token}" unless parameterizing_rule
bindings = Binding.new(parameterizing_rule, token.args)
lhs_s_value = lhs_s_value(token, bindings)
if (created_lhs = parameterizing_rule_resolver.created_lhs(lhs_s_value))
@replaced_rhs << created_lhs
else
lhs_token = Lrama::Lexer::Token::Ident.new(s_value: lhs_s_value, location: token.location)
@replaced_rhs << lhs_token
parameterizing_rule_resolver.created_lhs_list << lhs_token
parameterizing_rule.rhs_list.each do |r|
rule_builder = RuleBuilder.new(@rule_counter, @midrule_action_counter, lhs_tag: token.lhs_tag || parameterizing_rule.tag)
rule_builder.lhs = lhs_token
r.symbols.each { |sym| rule_builder.add_rhs(bindings.resolve_symbol(sym)) }
rule_builder.line = line
rule_builder.precedence_sym = r.precedence_sym
rule_builder.user_code = r.resolve_user_code(bindings)
rule_builder.complete_input
rule_builder.setup_rules(parameterizing_rule_resolver)
@rule_builders_for_parameterizing_rules << rule_builder
end
end
when Lrama::Lexer::Token::UserCode
prefix = token.referred ? "@" : "$@"
tag = token.tag || lhs_tag
new_token = Lrama::Lexer::Token::Ident.new(s_value: prefix + @midrule_action_counter.increment.to_s)
@replaced_rhs << new_token
rule_builder = RuleBuilder.new(@rule_counter, @midrule_action_counter, i, lhs_tag: tag, skip_preprocess_references: true)
rule_builder.lhs = new_token
rule_builder.user_code = token
rule_builder.complete_input
rule_builder.setup_rules(parameterizing_rule_resolver)
@rule_builders_for_derived_rules << rule_builder
else
raise "Unexpected token. #{token}"
end
end
end
def lhs_s_value(token, bindings)
s_values = token.args.map do |arg|
resolved = bindings.resolve_symbol(arg)
if resolved.is_a?(Lexer::Token::InstantiateRule)
[resolved.s_value, resolved.args.map(&:s_value)]
else
resolved.s_value
end
end
"#{token.rule_name}_#{s_values.join('_')}"
end
def resolve_inline(parameterizing_rule_resolver)
rhs.each_with_index do |token, i|
if inline_rule = parameterizing_rule_resolver.find_inline(token)
inline_rule.rhs_list.each_with_index do |inline_rhs|
rule_builder = RuleBuilder.new(@rule_counter, @midrule_action_counter, lhs_tag: lhs_tag, skip_preprocess_references: true)
resolve_inline_rhs(rule_builder, inline_rhs, i)
rule_builder.lhs = lhs
rule_builder.line = line
rule_builder.user_code = replace_inline_user_code(inline_rhs, i)
rule_builder.complete_input
rule_builder.setup_rules(parameterizing_rule_resolver)
@rule_builders_for_inline_rules << rule_builder
end
end
end
end
def resolve_inline_rhs(rule_builder, inline_rhs, index)
rhs.each_with_index do |token, i|
if index == i
inline_rhs.symbols.each { |sym| rule_builder.add_rhs(sym) }
else
rule_builder.add_rhs(token)
end
end
end
def replace_inline_user_code(inline_rhs, index)
return user_code if inline_rhs.user_code.nil?
return user_code if user_code.nil?
code = user_code.s_value.gsub(/\$#{index + 1}/, inline_rhs.user_code.s_value)
Lrama::Lexer::Token::UserCode.new(s_value: code, location: user_code.location)
end
def numberize_references
# Bison n'th component is 1-origin
(rhs + [user_code]).compact.each.with_index(1) do |token, i|
next unless token.is_a?(Lrama::Lexer::Token::UserCode)
token.references.each do |ref|
ref_name = ref.name
if ref_name
if ref_name == '$'
ref.name = '$'
else
candidates = ([lhs] + rhs).each_with_index.select {|token, _i| token.referred_by?(ref_name) }
if candidates.size >= 2
token.invalid_ref(ref, "Referring symbol `#{ref_name}` is duplicated.")
end
unless (referring_symbol = candidates.first)
token.invalid_ref(ref, "Referring symbol `#{ref_name}` is not found.")
end
if referring_symbol[1] == 0 # Refers to LHS
ref.name = '$'
else
ref.number = referring_symbol[1]
end
end
end
if ref.number
# TODO: When Inlining is implemented, for example, if `$1` is expanded to multiple RHS tokens,
# `$2` needs to access `$2 + n` to actually access it. So, after the Inlining implementation,
# it needs resolves from number to index.
ref.index = ref.number
end
# TODO: Need to check index of @ too?
next if ref.type == :at
if ref.index
# TODO: Prohibit $0 even so Bison allows it?
# See: https://www.gnu.org/software/bison/manual/html_node/Actions.html
token.invalid_ref(ref, "Can not refer following component. #{ref.index} >= #{i}.") if ref.index >= i
rhs[ref.index - 1].referred = true
end
end
end
end
def flush_user_code
if (c = @user_code)
@rhs << c
@user_code = nil
end
end
end
end
end
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