On 03/23/2012 09:14 AM, Damian Conway wrote: >> it means we cannot do the same fuzziness for the endpoint, > > Except that we will be encouraging people to use: * >= $END > as their standard endpoint pattern, which will provide > most of the necessary fuzz.
and which will still surprise those people who are surprised by floating point inaccuracies. >> This discussion makes me think that maybe >> deducing geometric sequences is too much magic as well. > > Geometric sequence inference is fine on Ints and Rats. > > But, if we can't perform inferences involving Nums in a sound numerical > way (and it may well be that we can't, without taking a noticeable > performance hit), then I think that we would be better off limiting the > deduction of *both* arithmetic and geometric sequences to starting lists > that contain only Ints and Rats. Floating point numbers *can* represent a huge number of commonly used values without errors, and you can do error-free arithmetic operations on many of them. Excluding Nums from automatic deduction feels like an unnecessary pessimization or stigmatization, especially if you consider that writing a number like 0.001 in your program gives a Rat by default not a Num. Most of the time you only get a Num in Perl 6 if you consciously decide to write one, in which case you should also be well aware of the limitations of FP math. At least in #perl6 I've never seen anybody try to write an auto-deduced sequence, and fail because of floating-point errors. Cheers, Moritz
