# Read the next sequence of non whitespace characters.
	#
	# Leading whitespace characters are skipped.
	# The first whitespace character that follows the result is consumed.
	#
	# An empty string is returned if the end of the file or an error is encounter.
	#
	# ~~~
	# var w = new StringReader(" Hello, \n\t World!")
	# assert w.read_word == "Hello,"
	# assert w.read_char == '\n'
	# assert w.read_word == "World!"
	# assert w.read_word == ""
	# ~~~
	#
	# `Char::is_whitespace` determines what is a whitespace.
	fun read_word: String
	do
		var buf = new FlatBuffer
		var c = read_nonwhitespace
		if c != null then
			buf.add(c)
			while not eof do
				c = read_char
				if c == null then break
				if c.is_whitespace then break
				buf.add(c)
			end
		end
		var res = buf.to_s
		return res
	end