Ken Clements:
So go ahead J. R., add it <analog
computers> to the list.
No. Please wait. Let us ponder.
(Is J.R.'s mind digital or not?)
- s.
___________________________
O-machines (Turing, 1938-1939) are Turing machines (1936)
augmented with one or more primitive operations each
of which returns the values of some function that is not
Turing-machine computable.
Each additional primitive operation is made available
by a black box: the "oracle".
One particular O-machine, the halting function machine,
can compute many functions that are not Turing-machine
computable.
Speculation as to whether there may actually be physical
processes that cannot be simulated by a (digital) machine
stretches back over at least four decades (Da Costa and
Doria 1991; Doyle 1982; Geroch and Hartle 1986; Komar 1964;
Kreisel 1967, 1974; Penrose 1989 and 1994; Pour-El 1974;
Pour-El and Richards 1979 and 1981; Scarpellini 1963;
Stannett 1990; Vergis et al 1986).
But if such processes do exist then perhaps future engineers
will use them to implement some O-machine.
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