[Python-ideas] Python Numbers as Human Concept Decimal System

[Oscar Benjamin]

On 10 March 2014 15:31, Steven D'Aprano <steve at pearwood.info> wrote:
> On Mon, Mar 10, 2014 at 02:05:22PM +0000, Oscar Benjamin wrote:
>
>> This is what I've been thinking about. Most non-expert users will be
>> very happy with Decimal64 and a single fixed context. There could be a
>> separate type called decimal64 in builtins that always used the same
>> standard context. Literals could create decimal64 instances.
>>
>> Where this would get complicated is for people who also use the
>> Decimal type. They'd need to keep track of which objects were of which
>> type and so decimal literals might seem more annoying than useful.
>
> Hmmm. I don't think this should necessarily be complicated, or at least
> no more complicated than dealing with any other mixed numeric types. If
> you don't want to mix them, don't mix them :-)

Exactly. It just means that you wouldn't want to use the literals in
code that actually uses the decimal module. Consider:

if some_condition:
    x = 1d
else:
    x = Decimal(some_string)
# ...
y = x / 3

So now x / 3 rounds differently depending on whether x is a decimal64
or a Decimal. I probably don't want that. The solution: coerce to
Decimal. But then why did I bother with the Decimal literal anyway?
Decimal(1d) is hardly better than Decimal('1').


Oscar