AMDG Terry Golubiewski wrote:

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Warning: untested code

typedef quanttyus::foot_base_unit::unit_type Length; Length x(2.0 * m);

Ok. That makes Length represent "feet" But I want Length to remain represented as an si::length, but input "ft" into it and convert to "ft" to print.

// static const si::length ft = ???; typedef quantitysi::length Length; Length x = 3.0 * ft; cout << "x=" << convert_to_ft(x) << endl;

typedef quantityus::foot_base_unit::unit_type convert_to_ft; In Christ, Steven Watanabe

AMDG Terry Golubiewski wrote:

Got it! Now the other part...

typedef quantitysi::length Length; Length x = 3.0 * ft;

If x is an SI unit, how can I convert from "ft"? I'm missing something, but I'm not sure what.

First define ft as static const us::foot_base_unit::unit_type ft; Then Length x(3.0 * ft); should work. In Christ, Steven Watanabe

Length x = 3.0 ft did not compile, see below... terry #include #include #include #include #include <iostream> #include <iomanip> using namespace std; using namespace boost; using namespace boost::units; int main() { typedef quantitysi::length Length; static const si::length m = si::meter; Length x = 2.0 * m; // This works! cout << x << endl; typedef us::foot_base_unit::unit_type foot_unit; static const foot_unit ft; Length y = 3.0 * ft; // This does not compile :o( cout << y << endl; return 0; } // main // Compiler output... tjg.cpp using native typeof tjg.cpp(21) : error C2440: 'initializing' : cannot convert from 'units::quantity' to 'units::quantity<Unit>' with [ Unit=units::unit< units::list< units::dim>, units::dimensionless_type >, units::heterogeneous_system< units::heterogeneous_system_impl< units::list< units::heterogeneous_system_dim< units::scaled_base_unit< units::us::yard_base_unit, units::scale<3, units::static_rational<-1>> >, units::static_rational<1> >, units::dimensionless_type >, units::list< units::dim>, units::dimensionless_type >, units::dimensionless_type > >

, Y=double ] and [ Unit=units::si::length ] Constructor for class 'units::quantity<Unit>' is declared 'explicit' with [ Unit=units::si::length ]

Yep, that's it. Sorry. I thought they were equivalent. Hmm. Could you please point me to somewhere that explains the difference between implicit and explicit construction? terry ----- Original Message ----- From: "Matthias Schabel" Newsgroups: gmane.comp.lib.boost.user To: Sent: Wednesday, May 19, 2010 7:31 PM Subject: Re: [units] How to assign "ft" to an si::length?

Explicit construction works, but assignment (which is implicit) does not...that's why Steven keeps recommending the explicit constructor - XX(3.0*ft) - syntax.

Matthias

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Length x = 3.0 ft did not compile, see below...