I'd like to echo what Chris is saying. It was a big annoyance with Numeric to make it so hard to preserve the array type in ordinary expressions.
Perry On Jan 17, 2013, at 8:04 PM, Chris Barker - NOAA Federal wrote: > On Thu, Jan 17, 2013 at 6:26 AM, Matthew Brett <matthew.br...@gmail.com> > wrote: > >> I am starting to wonder if we should aim for making >> >> * scalar and array casting rules the same; >> * Python int / float scalars become int32 / 64 or float64; > > aren't they already? I'm not sure what you are proposing. > >> This has the benefit of being very easy to understand and explain. It >> makes dtypes predictable in the sense they don't depend on value. > > That is key -- I don't think casting should ever depend on value. > >> Those wanting to maintain - say - float32 will need to cast scalars to >> float32. >> >> Maybe the use-cases motivating the scalar casting rules - maintaining >> float32 precision in particular - can be dealt with by careful casting >> of scalars, throwing the burden onto the memory-conscious to maintain >> their dtypes. > > IIRC this is how it worked "back in the day" (the Numeric day? -- and > I'm pretty sure that in the long run it worked out badly. the core > problem is that there are only python literals for a couple types, and > it was oh so easy to do things like: > > my_arr = np,zeros(shape, dtype-float32) > > another_array = my_array * 4.0 > > and you'd suddenly get a float64 array. (of course, we already know > all that..) I suppose this has the up side of being safe, and having > scalar and array casting rules be the same is of course appealing, but > you use a particular size dtype for a reason,and it's a real pain to > maintain it. > > Casual users will use the defaults that match the Python types anyway. > > So in the in the spirit of "practicality beats purity" -- I"d like > accidental upcasting to be hard to do. > > -Chris > > -- > > Christopher Barker, Ph.D. > Oceanographer > > Emergency Response Division > NOAA/NOS/OR&R (206) 526-6959 voice > 7600 Sand Point Way NE (206) 526-6329 fax > Seattle, WA 98115 (206) 526-6317 main reception > > chris.bar...@noaa.gov > _______________________________________________ > NumPy-Discussion mailing list > NumPy-Discussion@scipy.org > http://mail.scipy.org/mailman/listinfo/numpy-discussion _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
