nil?

gistfile1.txt

module Lox
	class Environment
		def initialize(enclosing : Environment | Nil)
			@enclosing = enclosing
			@values = {} of String => Type
		end

		def initialize()
			initialize(nil)
		end

		def get(name : Token)
			value = @values.fetch(name.lexeme, nil)

			unless value.nil?
				return value
			end

			unless @enclosing.nil?
				return @enclosing.as(Environment).get(name)
			end

			raise RuntimeError.new(name, "Undefined variable '" + name.lexeme + "'.")
		end

	end
end