Patrick correctly observed: > On Rakudo on my system, sqrt(2) indeed produces a Num, > but since floating point arithmetic doesn't result in > sqrt(2) / 1 == 2 / sqrt(2), no geometric sequence is deduced > and the sequence fails with "unable to deduce sequence".

Although, arguably, that might be considered a bug. Not that sqrt(2) / 1 should == 2 / sqrt(2) of course, but that, when deducing a sequence we know we're comparing quotients, so we ought to allow for the inevitable loss of significant digits within the two preliminary division ops, and therefore compare the results with an suitably larger epsilon. That would not only be computational more justifiable, I suspect it might also produce more "least surprise". ;-) Damian