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Versions: 7
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Stored size: 1.47 KB
Contents
# TODO: Validate position is not over rule rhs
require "forwardable"
module Lrama
class States
class Item < Struct.new(:rule, :position, keyword_init: true)
extend Forwardable
def_delegators "rule", :lhs, :rhs
# Optimization for States#setup_state
def hash
[rule_id, position].hash
end
def rule_id
rule.id
end
def empty_rule?
rule.empty_rule?
end
def number_of_rest_symbols
rhs.count - position
end
def next_sym
rhs[position]
end
def next_next_sym
rhs[position + 1]
end
def previous_sym
rhs[position - 1]
end
def end_of_rule?
rhs.count == position
end
def beginning_of_rule?
position == 0
end
def start_item?
rule.initial_rule? && beginning_of_rule?
end
def new_by_next_position
Item.new(rule: rule, position: position + 1)
end
def symbols_before_dot
rhs[0...position]
end
def symbols_after_dot
rhs[position..-1]
end
def to_s
"#{lhs.id.s_value}: #{display_name}"
end
def display_name
r = rhs.map(&:display_name).insert(position, "•").join(" ")
"#{r} (rule #{rule_id})"
end
# Right after position
def display_rest
r = rhs[position..-1].map(&:display_name).join(" ")
". #{r} (rule #{rule_id})"
end
end
end
end
Version data entries
7 entries across 7 versions & 1 rubygems