Is there an edge from element to t?

var pos = new POSet[String]
pos.add_chain(["A", "B", "C", "D"])
assert     pos["B"] <= "D"
assert     pos["B"] <= "C"
assert     pos["B"] <= "B"
assert not pos["B"] <= "A"

Property definitions

poset $ POSetElement :: <=
	# Is there an edge from `element` to `t`?
	#
	# ~~~~
	# var pos = new POSet[String]
	# pos.add_chain(["A", "B", "C", "D"])
	# assert     pos["B"] <= "D"
	# assert     pos["B"] <= "C"
	# assert     pos["B"] <= "B"
	# assert not pos["B"] <= "A"
	# ~~~~
	fun <=(t: E): Bool
	do
		return self.tos.has(t)
	end
lib/poset/poset.nit:591,2--604,4