# Replace a `macro` by a streamable `replacement`.
	#
	# REQUIRE `has_macro(name)`
	#
	#     var tpl = new TemplateString("Hello %NAME%!")
	#     tpl.replace("NAME", "Dave")
	#     assert tpl.write_to_string == "Hello Dave!"
	fun replace(name: String, replacement: Writable) do
		assert has_macro(name)
		for macro in macros[name] do
			macro.replacement = replacement
		end
	end