[racket-dev] racket/date, SRFI-19, date construction

Oh! Good point!



On Fri, Jan 11, 2013 at 9:53 PM, Ryan Culpepper <ryanc at ccs.neu.edu> wrote:

> I don't know how important this is, but ideally serialized old SRFI-19
> dates should now deserialize as date*. I think that you can just restore
> the definition of deserialize-info:tm:date-v0 and change the second
> function (the cyclic value builder) to raise an error:
>
> (define deserialize-info:tm:date-v0
>   (make-deserialize-info
>    srfi:make-date
>    (lambda ()
>      (error 'deserialize-info:tm:date-v0 "cycles not allowed"))))
>
> and also restore the provide.
>
> Ryan
>
>
>
> On 01/11/2013 09:13 PM, Asumu Takikawa wrote:
>
>> On 2013-01-11 15:39:08 -0600, Robby Findler wrote:
>>
>>>     I think it would be great if you were to find backwards-compatible
>>>     ways to bring these two a little bit closer. Making them use the
>>>     same internal date struct, for example, would be a great thing.
>>>
>>
>> I wrote a patch to make both of these use the same structure, attached
>> to the e-mail. It seems to pass all of the srfi-19 and date tests (with
>> some tests changed where appropriate). Does it look alright?
>>
>> It turns out there was one (sort of) good reason for SRFI-19 to define
>> its own struct type: it used mutation for several functions. Racket's
>> date/date* are immutable. I just changed these to use functional update.
>>
>> Another thing: when a string is converted to a date, it's possible that
>> the format string only has time-of-day but no date specification.
>> Previously, this produced a srfi/19 date with '#t's but I've now
>> defaulted it to the start day of the Unix epoch (arbitrarily).
>>
>> Cheers,
>> Asumu
>>
>>
>>
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