Thoughts on IEEE P754

Sam Ruby rubys at intertwingly.net
Fri Aug 22 11:44:20 PDT 2008


On Fri, Aug 22, 2008 at 2:28 PM, Waldemar Horwat <waldemar at google.com> wrote:
> Sam Ruby wrote:
>> Waldemar Horwat wrote:
>>>
>>> Some tidbits about our embedding of decimal:
>>>
>>> - Contagion should be towards decimal if decimal and binary are mixed
>>> as operands.  5.3m + 1 should be 6.3m, not 6.3.  If we use 128-bit
>>> decimal, this also makes the behavior of heterogeneous comparisons
>>> (binary compared to decimal) sensible.
>>
>> What should 5.3m + 1.0000000000000001 produce?
>>
>> I also don't understand the heterogeneous comparisons comment.  What
>> should 1.0000000000000001 == 1.0000000000000001m produce?
>
> Depends.  There are many decimal formats.  Which decimal format and representation are you specifying?

Decimal128.  But the key to this question is the fact that the
binary64 floating point constant is indistinguishable from the value
1.

>    Waldemar

- Sam RUby


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