  We propose a notion of state distinguishability that does not refer to
probabilities, but rather to the ability of a set of states to serve as
programs for a desired set of gates. Using this notion, we reconstruct the
structural features of the task of state discrimination, such as the
equivalence with cloning and the impossibility to extract information from two
non-distinguishable pure states without causing a disturbance. All these
features express intrinsic links among operational tasks, which are valid
independently of the particular theory under consideration.
