On 5/21/2009 3:26 PM, Vaughan Pratt wrote: > Consider (x+c)^2 where c is 1/n in case a given Turing machine halts Oops, that should have been x^2 + c of course, sorry. Less significantly, replace "within n > 0 steps" by "at the n-th step (n > 0)" (so as to define n as a particular number). Vaughan