On Tue, Feb 8, 2022 at 2:25 PM Steven D'Aprano <st...@pearwood.info> wrote:
> On Mon, Feb 07, 2022 at 05:35:17PM -0800, Gregory P. Smith wrote: > > > CPython: yes. we use a double. > > Python the language: no. (float is single precision on many micropython > > platforms as it saves precious ram and performance, plus microcontroller > > fpu hardware like an M4 is usually single precision 32bit) > > If we are to *officially* support non-double floats, it would be nice if > sys.float_info were to tell us explicitly how wide the floats are rather > than having to try to reverse engineer it from the other information > there. > > A floating point expert can probably look at this: > > sys.float_info(max=1.7976931348623157e+308, max_exp=1024, > max_10_exp=308, min=2.2250738585072014e-308, min_exp=-1021, > min_10_exp=-307, dig=15, mant_dig=53, epsilon=2.220446049250313e-16, > radix=2, rounds=1) > > and immediately recognise that those values imply a 64-bit float, but I > expect most people will not. If Python the language is going to support > single, double, quad precision floats, and maybe even minifloats with > just 16 or even fewer bits, then can we please add a field to float_info > telling us how many bits the floats have? > There is no need to know how many bits it is. The meaningful information about precision and accuracy from a math point of view is already expressed in float_info. the size in bits isn't relevant. You can derive the size from that if you'd like and are willing to assume a binary format. binary_bits = ~mant_dig+log2(max_exp)... But that tells you less than sys.float_info. -gps
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