🚀 go-pugleaf

In article <12398@sun.udel.edu>, jms@sun.udel.edu (John Milbury-Steen) writes:
> [the 8-puzzle, any heuristics?  how about a Prolog program?]

A reasonable approach is to use the A* algorithm.  That requires an
estimate of the distance from the current position to a solution, and
a fairly common heuristic for that is to count the number of tiles
which are not in their final position.  A* is not _quite_ as trivial
as depth first search (although if you have the DEC-10 Prolog or
Quintus Prolog library(heaps) and library(ordsets) packages or
functional equivalents it's actually rather simple) but for a problem
like this where the search space has more cycles than you can shake
a stick at and isn't all that small even if you disregard the cycles,
the extra performance of A* is well worth having.

-- 
"private morality" is an oxymoron, like "peaceful war".