new BigDecimal(double) is Java API and does a full precision conversion.

double.toBigDecimal() is a GDK method and goes through "groovy"
conversion via toString() and thus truncates. It is used by "as".

If you want full precision use new BigDecimal or a cast. If not, use
"as" (or double.toBigDecimal).

The change (and there must be a JIRA somewhere and I'm pretty sure I
made the change) was that the cast used to do rounding, which is a Bad
Thing for doing arithmetic and was inconsitent with new BigDecimal(double).

The jira: http://jira.codehaus.org/browse/GROOVY-3171

There are of course many other related issues and discussion in the
past, but I'm pretty sure we've got it (at least more) correct now.

Jim

Ronny Løvtangen wrote:

> I would expect d.toBigDecimal() to preserve as much precision as possible.
> If this is not the case, I think at least the javadoc should say so. Current javadoc says "Transform a Number into a BigDecimal"
>
> I still find it hard to believe that d.toBigDecimal() and new BigDecimal(d) intentionally should produce different result.
>
> Ronny
>
> On Feb 9, 2010, at 4:35 PM, Jim White wrote:
>
>
>>Ronny Løvtangen wrote:
>>
>>
>>>Yes, I would expect all variants to produce the same result, so I guess it's not intended. I also tried with new BigDecimal(d)
>>>In both 1.6.5, 1.6.6 an 1.7.0, the result is 0.1411200080598672135234750157906091772019863128662109375.
>>
>>I don't recall whether there was a change at 1.6.5 or not, although I have a faint memory of doing something in that area.
>>
>>I don't agree though that all forms of coercion should give the same result.
>>
>>The assignment is doing a cast rather than a "groovy" (typical expected human-friendly result) conversion that "as" does and is full precision.
>>
>>When doing calculations there must be a way to get that, and I'm thinking there was a change for just that purpose.
>>
>>Unfortunately I can't look into this deeper at the moment. Perhaps someday we can just have a FAQ that points to the relevant paragraph in the spec...
>>
>>Jim
>>
>>
>>>Ronny
>>>On Feb 8, 2010, at 11:00 PM, Paul King wrote:
>>>
>>>>I suspect it isn't intended but haven't yet checked the related
>>>>Jiras that occurred around that time.
>>>>
>>>>Paul.
>>>>
>>>>Ronny Løvtangen wrote:
>>>>
>>>>
>>>>>Is this change in behavior from Groovy 1.6.5 to 1.6.6 and later intended, or not?
>>>>>Double d = Math.sin(3)
>>>>>BigDecimal b1 = d.toBigDecimal()
>>>>>BigDecimal b2 = d as BigDecimal
>>>>>BigDecimal b3 = d
>>>>>println d
>>>>>println b1
>>>>>println b2
>>>>>println b3
>>>>>Result, Groovy 1.6.5:
>>>>>0.1411200080598672
>>>>>0.1411200080598672
>>>>>0.1411200080598672
>>>>>0.1411200080598672
>>>>>Result, Groovy 1.6.6 and 1.7.0:
>>>>>0.1411200080598672
>>>>>0.1411200080598672
>>>>>0.1411200080598672
>>>>>0.1411200080598672135234750157906091772019863128662109375
>>>>>Ronny


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