[threeten-dev] lambda + threeten

[Xueming Shen]

We do have LocalDateTime.minusDays(long) to return LDT. Where does the 
DateTime
come from. It appears all three work.

"fluent"              .map(d -> (d.minusDays(days)))
long, field          .map(d -> (d.minus(days, DAYS)))
minusAdjuster   .map(d -> (d.minus(dd -> (dd.with(EPOCH_DAY, 
(dd.getLong(EPOCH_DAY)- days))))))

One of the reasons that I thought the API provides too many ways to do 
the same thing.

-sherman

On 12/3/12 4:40 PM, Stephen Colebourne wrote:
>   .map(d -> (d.minusDays(days)))
> would not work (as the type is DateTime), but this will work:
>   .map(d -> (d.minus(days, DAYS)))
>
> It would be worth exploring if generics could be added to 
> WithAdjuster/MinusAdjuster etc to allow lambda adjusters to capture 
> the actual target type, and thus allow methods like minusDays() to be 
> called. I suspect it doesn't work, but it should be tried.
>
> Stephen
>
>
> On 3 December 2012 18:48, Xueming Shen <xueming.shen at oracle.com 
> <mailto:xueming.shen at oracle.com>> wrote:
>
>
>     It's the test for the "fancy" functional interface :-) for
>     example, for
>     the "minus adjuster" here you can simply use
>
>                    .map(d -> (d.minusDays(days)))
>     instead of
>                    .map(d -> (d.minus(dd -> (dd.with(EPOCH_DAY,
>     (dd.getLong(EPOCH_DAY)- days))))))
>
>     And the test does nothing:-) it simply adds two days, print them
>     out, and then
>     map them back to the original data.
>
>     -Sherman
>
>
>     On 12/03/2012 10:32 AM, Roger Riggs wrote:
>>     Hi Sherman,
>>
>>
>>
>>     I don't know what the non-lambda code would look like but the
>>     lambda'fied
>>     code below is not good at revealing what the intent of the
>>     function is.
>>     It still needs comments.  So blog away.
>>
>>     Thanks,Roger
>>
>>>
>>>     -Sherman
>>>
>>>     --------------------------------------------------------------------
>>>
>>>             LocalDateTime now = LocalDateTime.now();
>>>             Random r = new Random();
>>>
>>>             DateTimeFormatter fmt =
>>>                 DateTimeFormatters.pattern("yyyy-MM-dd HH:mm:ss
>>>     [EEEE]");
>>>
>>>             int total = 100;
>>>             int days = 2;     // days to delay
>>>             int minMon = 2;
>>>             int maxMon = 6;
>>>
>>>             Streams.repeatedly(total, () -> (now.withYear(2012)
>>>     .withDayOfYear(r.nextInt(365) + 1)
>>>     .with(SECOND_OF_DAY, r.nextInt(86400))))
>>>                    .sorted((d1, d2) -> d1.compareTo(d2))
>>>     //             .filter(d -> (d.getMonthValue() >= minMon &&
>>>     d.getMonthValue() <= maxMon))
>>>                    .tee(d -> {System.out.printf(" %-30s ",
>>>     fmt.print(d));})
>>>                    .map(d -> (d.with(dd -> (dd.with(EPOCH_DAY,
>>>     dd.getLong(EPOCH_DAY) + days)))))
>>>                    .tee(d -> {System.out.printf(" -->   %-30s ",
>>>     fmt.print(d));})
>>>                    .map(d -> (d.minus(dd -> (dd.with(EPOCH_DAY,
>>>     (dd.getLong(EPOCH_DAY)- days))))))
>>>                    .forEach(d -> {System.out.printf(" -->  
>>>     %-30s%n", fmt.print(d));});
>>>
>>
>>     -- 
>>     Thanks, Roger
>>
>>     Oracle Java Platform Group
>>
>>     Green Oracle <http://www.oracle.com/commitment> Oracle is
>>     committed to developing practices and products that help protect
>>     the environment
>>
>
>