Re: [Boost-users] [units] implicit type conversions to specific unit quantity

Subject: Re: [Boost-users] [units] implicit type conversions to specific unit quantity
From: Michael Powell (mwpowellhtx_at_[hidden])
Date: 2015-08-15 13:18:53

On Sat, Aug 15, 2015 at 12:32 PM, Michael Powell <mwpowellhtx_at_[hidden]> wrote:
> Hello,
>
> I'd like to convert from an SI length quantity to a US inches
> quantity. I believe the following snippet will do what I want it to,
> but wanted to clarify if that was the case:
>
> http://www.boost.org/doc/libs/1_59_0/doc/html/boost_units/Quantities.html
>
> I am referencing the online docs, but needed some clarity in actually
> how to go about using it in practice:
>
> <code>
> using boost::units::si::meter_base_unit;
> using boost::units::us::inch_base_unit;
>
> // i.e. 0.3048 * 12 (inches/feet, feet/meter)
> BOOST_UNITS_DEFINE_CONVERSION_FACTOR(inch_base_unit, meter_base_unit,
> double, 3.6576);
>
> //...
>
> quantity<inch_unit> to_inches_length_quantity(quantity<length> const & L) {
>     const quantity<inch_unit::unit_type> result_(L);
>     return result_;
> }
> </code>

I'm not sure I wasn't at a similar spot as with Ryan in a prior thread.

https://groups.google.com/forum/#!topic/boost-list/3kx_vFpzHSc

I was able to move the typedefs, etc, into a source file, and the
external symbols resolved properly.

Also, I'm not positive, the inches <-> meters length conversion isn't
already defined? At least some errors leading up to this point seem to
suggest that perhaps it is. Although I want to be careful that meters
<-> inches is correct and that yards aren't getting in the way.

> Just besides that, there isn't a cleaner way of doing it? Some have
> mentioned going as far as creating a whole other system for my
> calculator's purposes, for example.
>
> Thank you...
>
> Best regards,
>
> Michael Powell