Re: [boost] [gsoc 2013] draft proposal for chrono::date

5 May 2013

      Le 05/05/13 04:19, Rob Stewart a écrit :
...
On May 4, 2013, at 4:15 PM, "Vicente J. Botet Escriba"  wrote:
...
I have just extracted from my current interface some of the functions that we could have in a full featured date class.
class date;
date today();
I'd expect to be able to influence the time zone.
Boost.DateTime provides time zone management, but as far as I know it 
has been a nightmare to maintain it.
If someone knows of some portable 3pp library that we could include in 
Boost helping on time zone management I could include it, but developing 
it is not on my priorities.
Maybe someone wants to do it or mentor a GSoC for the next year.
The best I can do for the time been is to provide UTC and local 
timezones. This doesn't mean that the standard could not provide more.
...
...
class date {
public:
  // construct/copy/destruct
  date(); // |year(0)/jan/1|
  date(year, month, day);
  date(year, month, day, no_check_t);
  // and all the usual combinations
I'm warming up to the checked/unchecked dichotomy between date and make_date(), though the latter can be used for multiple date types and all must be checked or unchecked alike.
...
bool set_if_valid_date(year, month, day);
This seems odd. I'd prefer set(), with an exception and, maybe, try_set(), returning bool.
Yes, the name is not the best. try_set would be better.
...
day day() const; // or explict operator day(); the same for the other accessors.
I'd expect one or the other. day() is probably better, since day can offer an explicit, converting constructor to get the effect of the operator. That simplifies the date I/F a little.
Let me show the usage:

dt.day()

or

day(dt)

What do you prefer? Couldn't both be provided?

I have one possible non-member addition. I'm trying to see how to 
compare two dates of different date types.
Should the user convert explicitly before comparing ?

days_date d1;
ymd_date d2;

if (d1 == days_date(d2))

versus

if (ymd_date(d1) == d2)

or should the operator choose the conversion?

if (d1 == d2)

This is surely not too important as the user would use the same date 
type while comparing comparing dates.

Best,
Vicente