On Wed, Apr 6, 2022 at 5:11 AM Oscar Benjamin <oscar.j.benja...@gmail.com> wrote:
> > >Personally I think giving Decimal a global context was a mistake, [...] > I agree here -- though honestly, I think the benefits of Decimal are often misrepresented. Interestingly, the variable precision is the real bonus, not the decimal representation. Anyhoo ... > > I'd be curious to know what alternatives you see. When a user writes `x > + y` with both `x` and `y` instances of `decimal.Decimal`, the decimal > module needs to know what precision to compute the result to What do other variable precision systems do? With a quick read, it looks like gmpy2 does something similar :-( > (as well as what rounding mode to use, etc.). Absent a thread-local > context or task-local context, where would that precision information come > from? > Why is that absent? -- it seems a task local and/or thread local context is exactly what should be done. > One possibility is to attach the context information to the instances > so it's like: > That seems the obvious thing to me -- a lot more like we already have with mixing integers and floats, and/or mixing different precision floats in other languages (and numpy). Different, as this wouldn't be type based, but if clear rules are established, then it would be do-able. At least it would probably fit the maxim: The easy stuff should be easy, the hard stuff should be possible. Perhaps even something as simple as "Preserve the precision of the highest precision operand" would go a long way. Realistically do many users want to use many different contexts and > regularly switch between them? I expect the common use case is wanting > to do everything in a particular context that just isn't the default > one. > I don't know that that's true in the least -- sure, for a basic script, absolutely, but PYthon has become a large ecosystem of third party packages -- people make a LOT of large systems involving many complex third party packages -- the builder of the system may not even know a package is using Decimals -- let alone two different third party packages using them in very different ways -- it's literally impossible for the developer of package A to know how package B works or that someone might be using both. Then put all this behind a multithreading web server, and you have a recipe for chaos. -CHB -- Christopher Barker, PhD (Chris) Python Language Consulting - Teaching - Scientific Software Development - Desktop GUI and Web Development - wxPython, numpy, scipy, Cython
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