Editing Computable function (section)

===Relative computability===

The notion of computability of a function can be [[relative computability|relativized]] to an arbitrary [[Set (mathematics)|set]] of [[natural number]]s ''A''. A function ''f'' is defined to be '''computable in ''A''''' (equivalently '''''A''-computable''' or '''computable relative to ''A''''') when it satisfies the definition of a computable function with modifications allowing access to ''A'' as an [[oracle (computability)|oracle]]. As with the concept of a computable function relative computability can be given equivalent definitions in many different models of computation. This is commonly accomplished by supplementing the model of computation with an additional primitive operation which asks whether a given integer is a member of ''A''. We can also talk about ''f'' being '''computable in ''g''''' by identifying ''g'' with its graph.