On 15 February 2014 09:12, meekerdb <[email protected]> wrote: > On 2/14/2014 8:14 AM, Bruno Marchal wrote: > > With some definition of the abacus, it is Turing universal. With others it > is not. > The slide rules is not Turing universal. You can add and multiply > approximation of natural numbers only, or, if you want, you can > analogically add and multiply the real numbers, and that is not Turing > universal. (That is not entirely obvious). > > > That's an interesting point to me (I own a collection of circular slide > rules). Of course you can add and subtract on a slide rule as well as > multiply, divide, exponentiate, and compute the value of other functions > encoded on the rule (sin, tan), but the rule doesn't do it by itself; you > provide the sequence of operations consisting of reading a cursor and > moving the rule. So why would that not be Turing universal? >
I would guess because it isn't digital, but analogue? 'cause Turing machines use discrete symbols, while slide rules use a continuous scale? -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/groups/opt_out.
