Thanks Steven. I now see the problem arises from using si::dimensionless with nautical::length (The error message I get depends on the included header files but is related to the operator+ (when absolute.hpp is included) or the lack of a specialized add_typeof_helper in case that for example si/area.hpp is included). I guess my misconception was that I silently assumed that the 'dimensionless' type was acting as a normal double, reinforced by the fact that the line with the pure multiplication (nm1 = d*nm2;) does compile OK. The documentation says that " Because dimensionless quantities have no associated units, they behave as normal scalars, and allow implicit conversion to and from the underlying value type or types that are convertible to/from that value type". I intended to use my TDimless type as a 'generic' type for dimensionless quantities, but I now understand these quantities still need to be related to a 'system' and every system would need its own dimensionless type, even though there is no relation to the base units that define the system. Would I need to explicitly define conversions (e.g. BOOST_UNITS_DEFINE_CONVERSION_FACTOR(nautical::dimensionless, si::dimensionless, double, 1.0); or is there a more elegant way to use dimensionless quantities across systems? Thanks again, Pieter -----Original Message----- From: Steven Watanabe [mailto:watanabesj@gmail.com] Sent: Friday, September 23, 2011 17:06 To: boost@lists.boost.org Subject: Re: [boost] Boost.Units problem with user-defined units and dimensionless quantities AMDG On 09/21/2011 12:29 PM, Pieter wrote:

I am having some trouble using user-defined units and dimensionless once. Consider the example (taken straight from the documentation) that defines nautical miles (added at the bottom).

When I do the following on VS2010:

typedef quantity<boost::units::nautical::length> TDistanceInNMI; typedef quantity<dimensionless> TDimLess;

TDistanceInNMI nm1,nm2,nm3; TDimLess d;

nm1 = nm2 + nm3; // compiles OK nm1 = d*nm2; // compiles OK nm1 = nm2 + d*nm3; // does not compile, claims there is no operator+ defined

I suppose I might have to add a dimensionless type to the 'nautical' system, or have some misconceptions on how this should work. I tried adding the following line (mimicking some of the internal stuff) but that did not due to trick:

typedef unit<dimensionless_type,system> dimensionless;

I'm surprised that this doesn't work. It seems to work when I try it. The attached compiles with MSVC 2010.

Could anyone tell me whether there is there anything I need to define to make this work?

In Christ, Steven Watanabe