Re: [boost] constrained_value question

From: Neal Becker (ndbecker2_at_[hidden])
Date: 2008-05-21 19:25:47

Robert Kawulak wrote:

>> From: Neal Becker
>> Robert Kawulak wrote:
>> > You can write error policy:
>> > 
>> > struct stretchy_policy {
>> >     template <typename V, typename C>
>> >     void operator () (const V &, const V & new_val, C & constraint)
>> >     {
>> >         if( constraint.is_below(new_val) )
>> >             constraint.lower_bound() = new_val;
>> >         else
>> >             constraint.upper_bound() = new_val;
>> >     }
>> > };
> [snip]
>> It wouldn't be part of the error_policy, since the extrema
>> might be within
>> bounds and error_handler wouldn't then be invoked.
> 
> I'm not sure I get what's your point here. The idea is to make an error
> policy, which, when "error" is detected (out-of-bounds value assigned),
> corrects the bounds to make the new value fit within them. This way the
> bounds actually are the extrema. Of course, if the error handler is not
> invoked, this means that the value is between the past extrema and
> therefore no extremum is updated.
> 
OK, I see the confusion.  My idea was to record extrema _in addition to_
some other error policy.  For example, throw if out of bounds, but also
collect extrema data.  In this case the error policy would not normally
happen.