Re: [Boost-users] more Boost::Units questions

Subject: Re: [Boost-users] more Boost::Units questions
From: Matthias Schabel (boost_at_[hidden])
Date: 2009-01-09 18:33:08

> My biggest issue is that my recent software development experience  
> has involved using Java much more than C++ and I'm trying to learn  
> how to use a C++ library that makes pretty heavy use of templates.  
> Is there a tutorial somewhere that shows examples of doing basic  
> things with this library? The kind of things

The examples directory has simple, functional demonstrations of just  
about every type of functionality that anyone has wanted to date.

> - What is the difference between a "measurement" and a "quantity"?  
> Is it that the former doesn't specify a unit?

measurement is just a toy class to demonstrate that you can integrate  
units with non-trivial UDTs.

> - Does the library provide functions for converting between  
> different units? ... for example, converting from miles to  
> kilometers. If not, is there a recommended way to do this?

Dimensionally consistent quantities can be converted by explicit  
construction or through conversion_factor. See the examples I listed  
earlier.

> - Can I only add quantities that have the same unit or can I add  
> ones with different units and the library will handle conversions  
> for me?

Any dimensionally-consistent quantities may be combined, but you need  
to stipulate the conversion path yourself - the library specifically  
disables implicit conversions because these are impossible to make  
consistent.

> - How can I extract the numeric value from a quantity?

The value() member function.

> - How can I extract the unit type from a quantity?

Did you look at the documentation for class quantity? Use the  
unit_type typedef.

I really strongly recommend you go through the example code. Just  
about everything is in there and is reasonably well commented.

Matthias