Re: [boost] Interest in dimension/unit-checking library?

From: Deane Yang (deane_yang_at_[hidden])
Date: 2005-10-20 14:39:15

<jaw drops>

If you really do use C++ to do this type of stuff, then I definitely 
concede the point. Implicit unit casting is definitely useful in your 
example.

Andy Little wrote:
> "Deane Yang" wrote
> 
>> It could be just me, but I'd like to be at least warned if I manage to
>> write code that contained
>>
>> quantity_in_inches + quantity_in_meters
>>
>> or even
>>
>> quantity_in_millimeters - quantity_in_kilometers
>>
>> Both to me are signs that something went wrong.
> 
> Actually I had just a problem the other day where the conversion came in handy.
> i wanted to find postage for an item to go on ebay. I had a kitchen scales that
> works in lb and oz, and which was also not adequte to weigh the item which was
> around 15 kg. in weight. So I got a plank of wood and put one end to the floor
> and the other to the scales. Then I put the ebay-item on some way down the wood
> so I didnt max out the scales.
> Then I did a quick C++ program with pqs library to get the result. It sure was
> easy not having to do all the conversions by hand. Heres the program:
> 
> #include <pqs/pqs.hpp>
> int main()
> {
>     pqs::length::m L1(1.57); // ebay_item  disance along beam to scale
>     pqs::length::m L2(.47); // ebay-item distance to beeam end on floor
>     pqs::length::m L = L1 + L2; // total beam length
>     pqs::mass::kg m1 = pqs::mass::lb(9) + pqs::mass::oz(6); // mass read by
> scales with item
>     pqs::mass::kg m2 = pqs::mass::lb(2) + pqs::mass::oz(10); // mass of beam
> only
>     pqs::mass::kg m = m1 - m2; // mass on scales to due ebay-item
>     pqs::mass::kg result = m * L / L2;  // scale by  moment
>     std::cout << result <<'\n';
> }
> 
> This also occurs with user input which often requires a conversion from e.g
> imperial units to S.I. units.
> 
> cheers
> Andy Little
> 
> 
> 
> 
> 
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