State-dependent cloning machines that have so far been considered either de
terministically copy a set of states approximately or probabilistically cop
y them exactly. In considering the case of two equiprobable pure states, we
derive the maximum global fidelity of N approximate clones given M initial
exact copies, where N>M. We also consider strategies that interpolate betw
een approximate and exact cloning. A tight inequality is obtained that expr
esses a trade-off between the global fidelity and success probability. This
inequality is found to tend, in the limit N --> infinity, to a known inequ
ality that expresses the trade-off between error and inconclusive result pr
obabilities for state-discrimination measurements. Quantum-computational ne
tworks are also constructed for the kinds of cloning machine we describe. F
or this purpose, we introduce two gates: the distinguishability transfer an
d state separation gates. Their key properties are described and we show ho
w they may be decomposed into basic operations.