require_relative "error" module Lox class Environment attr_reader :values, :enclosing def initialize(enclosing = nil) @enclosing = enclosing @values = {} end def define(name, value) @values[name] = value end def ancestor(distance) env = self distance.times { env = env.enclosing } env end def get(token) name = token.lexeme if @values.has_key?(name) @values[name] elsif @enclosing @enclosing.get(token) else raise RuntimeError.new(token, "Undefined variable '#{name}'.") end end def get_at(distance, name) ancestor(distance).values.fetch(name) end def assign(name, value) lexeme = name.lexeme if @values.has_key?(lexeme) @values[lexeme] = value elsif @enclosing @enclosing.assign(name, value) else raise RuntimeError.new(name, "Undefined variable '#{lexeme}'.") end end end end