On Thu, Mar 5, 2020 at 5:55 AM André Roberge <andre.robe...@gmail.com>
wrote:
>
>
> On Thu, Mar 5, 2020 at 5:29 AM Steve Barnes <gadgetst...@live.co.uk>
> 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.
>>
>>
> SNIP
>>
>>
>>
>> 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
>>
>> ```
>>
>
> It is possible, and quite straightforward, to do this as an import hook or
> a custom encoding. I will try to do so and document it later today, and
> post it on this list.
>
>
> Quick **first draft**:
>>> from ideas.examples import decimal_math
>>> hook = decimal_math.add_hook()
>>> from ideas import console
>>> console.start()
Configuration values for the console:
source_init from ideas.examples.decimal_math
transform_source from ideas.examples.decimal_math
--------------------------------------------------
Ideas Console version 0.0.15. [Python version: 3.7.3]
~>> 0.1 + 0.2 == 0.3
True
~>> 0.1 * 10 == 1
True
~>> 0.1
Decimal('0.1')
~>> 0.1 + 0.100
Decimal('0.200')
Documentation at
https://aroberge.github.io/ideas/docs/html/decimal_math.html (This took
longer to write than the actual code.)
André Roberge
>
>
>>
>>
>> I do know that this goes against the explicit is better than implicit so
>> an alternative might be to have a flexible base modifier, something like:
>>
>> ```
>>
>> from decimal import DecimalBase as D
>>
>>
>>
>> a = 0D0.1 # These are all now decimals
>>
>> b = 0D0.2
>>
>> c = 0D0.3
>>
>> a + b == c # This now works
>>
>> ```
>>
>>
>>
>> Since anything like this would require overriding at least part of the
>> base interpreter I do not think that this is a suitable one for an external
>> PyPi library or at least some hooks in the interpreter would be required to
>> make it possible.
>>
>>
>>
>> Any thoughts, feedback, interest, expressions of horror? Or is this
>> already there and I have missed it?
>>
>>
>>
>> Steve Barnes
>>
>>
>>
>>
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>
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