On Thu, Mar 5, 2020 at 4:27 AM Steve Barnes <[email protected]> wrote:
> One of the lovely things about Python is that we have the capability to
> avoid issues such as the vagaries of the floating point type with libraries
> such as decimal and fractions. This is wonderous to me but comes with an
> issue that I suspect is limiting its usage. That issue is that you have to
> litter your code with constructors of those types, e.g.
>
>
>
> ```
>
> a = 0.1
>
> b = 0.2
>
> c = 0.3
>
> a + b == c # This doesn’t work but it is easy to forget why
>
> ```
>
> vs:
>
> ```
>
> from decimal import * # I know why this is bad but it comes straight from
> the examples
>
> a = Decimal("0.1") # Needs to be a string to avoid being temporarily a
> float
>
> b = Decimal("0.2") # Ditto
>
> c = Decimal("0.3") # Ditto
>
> a + b == c # Magic this works!
>
> ```
>
>
>
> While this works it is not very friendly to users and there will often be
> cases where people forget to quote the values, etc. and there are similar
> issues with using the fractions library and I am sure with others. I
> suspect that this is why the decimals library, and some others, is not used
> as widely as it possibly should be.
>
>
>
> Wouldn’t it be possible to have something along the lines of:
>
>
>
> ```
>
> from decimal import TreatFloatsAsDecimal
>
> @TreatFloatsAsDecimal
>
> a = 0.1 # These are all now decimals
>
> b = 0.2
>
> c = 0.3
>
> a + b == c # This now works
>
> ``
>
>
If you were going to do this you would probably need something like a
context manager to control the scope, such as:
with TreatFloatsAsDecimal:
a = 0.1 # decimal
b = 0.2 # decimal
c = 0.3 # decimal
d = 0.3 # float
I have been interested in something like this in the context of numpy
arrays, but I am not sure even that would even be possible under how the
python language works, and if it was I figured it was too complicated to be
worthwhile.
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