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

On May 6, 2013, at 10:10 AM, Howard Hinnant wrote:

On May 6, 2013, at 9:55 AM, "Vicente J. Botet Escriba" wrote:

...

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

...

...

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?

Any two explicit units should disambiguate. We could even take it more lax than that and still avoid ambiguity if desired.

+1

A warning though: We want to make the checked syntax more attractive than the unchecked syntax, else all dates will be unnecessarily unchecked in practice.

Separate types can handle the checked/unchecked difference, and both can be equally easy to use.

...

...

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

Agreed.

I agree, so long as the unit types convert to int, thereby allowing arithmetic operations. (I think that is implied above, but I wanted to be certain.) ___ Rob (Sent from my portable computation engine)