Modify state by applying action

The action comes from an earlier invocation of actions.

Property definitions

ai $ BacktrackProblem :: apply_action
	# Modify `state` by applying `action`
	# The `action` comes from an earlier invocation of `actions`.
	fun apply_action(state: S, action: A) is abstract
lib/ai/backtrack.nit:60,2--62,50

ai $ QueenProblem :: apply_action
	# The first free row become occupied with a queen placed where indicated.
	redef fun apply_action(rows, column)
	do
		rows.add column
	end
lib/ai/examples/queens.nit:85,2--89,4