# Is this string prefixed by `prefix`?
	#
	# ~~~
	# assert "abcd".has_prefix("ab")           ==  true
	# assert "abcbc".has_prefix("bc")          ==  false
	# assert "ab".has_prefix("abcd")           ==  false
	# ~~~
	fun has_prefix(prefix: String): Bool do return has_substring(prefix,0)