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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:
> 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.!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

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