Re: [Boost-users] Boost::Date_Time - Incr and Decr Operators

From: Jeff Garland (jeff_at_[hidden])
Date: 2007-02-12 15:23:21

Steve Johns wrote:
> Getting started with Boost::Date_Time ...
> 
> It seems that this is OK:
> 
> greg_year y1(2000);
> y1 = y1 + 1;
> 
> but this is not:
> 
> greg_year y1(2000);
> y1++;
 >
> I take it that the increment and decrement operators are not implemented for 
> greg_year (or the corresponding month, day, etc. types).

Right.

> Is this just incidental to the current implmentation, or is there some 
> particular architectural or domain reason why ++ and -- aren't in the mix?

Most users don't use greg_year much so it's never really come up.  That said, 
there would be some issues.  We'd need to specify this for greg_month to be 
symmetric.  So what would we do with this:

greg_month m(12);
m++; //wrap?
greg_year y(9999); //max year
y++; //exception I would guess?

So, the bottom line is that these ops aren't supported to try and keep the 
interface smaller.  And, in general, increment and decrement require a large 
amount of context that isn't necessarily obvious it was a good idea. BTW, are 
aware that you can do this?

date d(....);
years y(1);
y += years(2);
d += y;
d += week(20);

Jeff