[layer8]

That sounds like a more powerful variation of Excel's Goal Seek function. The latter however uses an iterative approximation approach. Given the non-exact nature of floating point, it would be interesting to see if numeric approximation can be combined with a Prolog-like resolution algorithm.

[tobmlt]

Yes indeed! Successful (caveat that term appropriately ;) versions of this prolog+floats idea have used interval analysis in the past. Anyway, yep you can do it, and it is fun!