# Re: [tlaplus] Mathematical puzzle modeling

Another solution, which I find easier to read: http://cs.unh.edu/~charpov/stone.tla

It probably requires more work from TLC but less thinking on my part!

MC

On Wednesday, February 4, 2015 at 7:56:27 PM UTC-5, Leslie Lamport wrote:
I just posted in the CodePlex repository a TLA+/TLC solution to this problem for arbitrary weight of stone and number of pieces.  The repository is at

Click on Source Code > examples > Stones.  However, I recommend trying to write such a solution yourself before looking at mine.

On Wed, Feb 4, 2015 at 1:48 PM, TLA Plus wrote:
Thanks for the puzzle.  It took me just a little more time to write a spec that allows TLC to solve the problem than to solve it myself.  (However, I had heard it before and so recreating the solution was easy.)  TLC found the solution in a few seconds.  I will leave this as a puzzle for readers to solve, and I hope others will do the same.  I therefore rejected an email someone just sent that reveals the solution, although not the TLA+ spec that allows TLC to solve it.  After TLC shows you the answer, the reasoning behind it becomes fairly obvious.

On Wed, Feb 4, 2015 at 1:15 PM, step...@xxxxxxxxx wrote:

A farmer has a 40 pound stone and a balance scale. How can he break the stone into 4 pieces so that, using those pieces and the balance scale, he can weigh out any integral number of pounds of corn from 1 pound through 40 pounds.
Who to use TLA+ to specify the problem and use TLC to find the solution?

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