Proper complexity function

Proper complexity function

A proper complexity function is a function "f" mapping a natural number to a natural number such that:
* "f" is nondecreasing;
* there exists a "k"-string Turing machine "M" such that on any input of length "n", "M" halts after O("n" + "f"("n")) steps, uses O("f"("n")) spaces, and output "s" "f"("n") consecutive blanks.

If "f" and "g" are two proper complexity functions, then "f" + "g", "fg", and 2"f", are also proper complexity functions.

Similar notions include honest function, space-constructible function, and time-constructible function.


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