Re: [boost] [chrono/date] Unit specifiers arithmetic

Le 06/05/13 15:34, Howard Hinnant a écrit :

On May 6, 2013, at 6:31 AM, "Vicente J. Botet Escriba" wrote:

...

Hi,

Moving from checked dates to unchecked ones by default and forcing to user the Unit specifiers year/month/day in any date constructor (even the unchecked ones) has some ugly consequences. Note that I was able to build an unchecked date as

date d(2013,5,6, no_check);

Given

year y; month m; day d;

the following will not compile now as the constructors expects a year but y+1 is an int.

date d(y+1, m, d);

The user needs to type

date d(year(y+1), m, d);

Is this what we want to provide to the user or should we add basic arithmetic on these unit specifiers? This is an example of where flexible ordering and implicit last unit starts to shine. Examples from my 2011 paper:

start = mon <= jan4/(d.year()-1);

date next_start = mon <= jan4/(start.year()+1);

Or translated to your example and syntax:

date d(d, m, y+1); // works because last unit can be int Last unit or any unit but only one?

If we start adding arithmetic to the unit specifier day, it becomes indistinguishable from a duration. Now it is possible that we could use durations as unit specifiers. -1

Vicente