Nondeterministic programming

http://www.ccs.neu.edu/home/dorai/t-y-scheme/t-y-scheme-Z-H-16.html#node_chap_14

by lfborjas • 15 years ago

64 17 15 years ago

ccs.neu.edu

yuvadam• 15 years ago

Nice, but I'm not sure I get it. There is no such thing as a concrete non-deterministic operation. How does the expression evaluate? If all the parameters are evaluated in order, there's nothing non-deterministic about it.

yogsototh• 15 years ago

There is no known real world non-deterministic Turing Machine. We could only simulate it using a deterministic Turing Machine (like a common computer).

Using this operator make the code really clear (IMHO) and I suppose it is its purpose.

Furthermore, if one day we discover an hardware able to be a non-deterministic Turing machine is discovered, the code will work.

[1]: I doubt such an hardware exists. But you could look about quantum computer for something close to what is a non-deterministic Turing machine.

szany2• 15 years ago

Navia Systems is designing nondeterministic hardware.

http://www.naviasystems.com/

calibraxis• 15 years ago

"Non-deterministic" is a somewhat technical term... Wikipedia gives a good explanation of what aspect of this operation makes it be called nondeterministic. (http://en.wikipedia.org/wiki/Nondeterministic_algorithm)

stiff• 15 years ago

It is non-deterministic in the sense that the program itself and its inputs are not sufficient to determine the program behavior, as the amb operator creates a set of "possible worlds" in which the same expression has different values. Of course to implement it on a traditional computer, one has to simulate this behavior and decide on some order of evaluation. In SICP, where this is discussed in more depth, one of the exercises asks the reader to modify amb to return a random choice instead of just the subsequent one and this expands the range of problems one can apply this technique to:

http://mitpress.mit.edu/sicp/full-text/book/book-Z-H-28.html... http://mitpress.mit.edu/sicp/full-text/book/book-Z-H-28.html...

rincewind• 15 years ago

In arc: http://arclanguage.org/item?id=6669

chrisjsmith• 15 years ago

SICP covers this too: http://mitpress.mit.edu/sicp/full-text/book/book-Z-H-28.html...

The references are better than the posted link.

I have found a couple of uses for this in the past and deparately tried to port the examples to C# (unsuccessfully).

shriphani• 15 years ago

I agree. I had to use NDP for solving a few CSPs recently. SICP was a godsend.

motxilo• 15 years ago

As a practical use, a while ago I "resolved" the Einstein's Riddle using this operator: http://ticsblog.com/2010/12/07/solving-einsteins-riddle-usin...

zwischenzug• 15 years ago

I don't understand the point of the solutions - why is a non-deterministic output of a function better than iterating over a list? If anything, it would be worse.

caioariede• 15 years ago

In ruby: http://www.randomhacks.net/articles/2005/10/11/amb-operator

lfborjas2• 15 years ago

Cool, I was wondering if it could be implemented in ruby; it's a shame that callcc isn't present anymore in ruby 1.9

lfborjas2• 15 years ago

I was wrong, ruby 1.9 has callcc back since 2009, you have to `require 'continuation'` now, though.

gromgull• 15 years ago

Isn't this just the prolog-ism of backtracking imported into other languages? Especially as long you just evaluate the options in order?

_delirium• 15 years ago

The article mentions that it's related, but somewhat simpler because it's "only" backtracking, versus Prolog's full logic programming:

The embedding recalls the continuation strategies used to implement Prolog-style logic programming, but is sparer because the operator provided is much like a Scheme boolean operator, does not require special contexts for its use, and does not rely on linguistic infrastructure such as logic variables and unification.

Nondeterministic programming

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