Re: [boost] units: review

From: Lewis Hyatt (lhyatt_at_[hidden])
Date: 2007-03-29 11:08:39

> for(quantity<SI::electric_potential> V = 1 * SI::volt; V != 
> 10*SI::volt; ++V)	{
> 		cout << "voltage is now at " << V << endl;
> 	}
> 
> I think this is perfectly natural, and should compile. Disallowing this 
> will force users of more complex types to create temporary objects in 
> cases where operator++ would render them unnecessary; I think this is 
> too restrictive.
> 

OK, I take it back, this shouldn't be supported. Code like this would be 
very confusing:

for(quantity<SI::electric_potential> V = 1 * SI::kilo * SI::volt;
     V != 10 * SI::kilo * SI::volt;
     ++V) cout << V << endl;

I guess in that case people might assume the ++ means add 1 kV, instead 
of 1V. Since the "natural" unit of increase depends on context, and 
people may not always know what the underlying units system is (eg, is 
mass in grams or kilograms?), this shouldn't be allowed.

-Lewis