Re: [Boost-users] Re: date-time

On Tue, 20 Jul 2004 21:45:19 -0400, Caleb Epstein wrote

On Tue, 20 Jul 2004 17:20:45 -0400, David Abrahams wrote:

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"Jeff Garland" writes:

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I've given in to user demand -- the default constructor to not_a_date_time will be in the 1.32 -- gregorian::date same story.

Why was that the right choice? It seems like an opportunity for bugs.

What would you propose as an alternative? I hope not the current system time, the acquisition of which can be a relatively expensive operation.

Oh my, never, no way. A certain famous vendor of C++ libraries made this mistake. Needless to say, I was none to happy when my scheduling application had to make 100K time values and we found we were burning all our time reading the system clock to get a value that would be overwritten in a few instructions. In a future version this company created a whole new time class and deprecating the original solution.... There's probably a design principle here like: value object constructors shouldn't have expensive side effects like making system calls.

I for one prefer the not_a_date_time option.

This should be about as expensive as boost::int64_t v = 0; depending on how good your compiler is at munching template code ;-) Jeff