Matthias Schabel said: (by the date of Mon, 28 Nov 2011 14:13:55 -0800)
The first line compiles correctly using Boost 1.48; I don't know when the fix was made.
Thanks, I'll upgrade to 1.48 before going forward :)
However, you also have an error in the second line; alpha is not a reciprocal_area : kg * (1/s) / (kg m^2/s)^1/2 = kg^1/2 s^-1/2 m^-1. Of course, this makes the third line incorrect as well; an example of the power of Boost.Units, I guess...
oh, yes. Definitely a power of Boost.Units, and the best reason to use it! Indeed I have a mistake here. I had a little different formula few pages back in my notebook, then I rewrote it to new place intrudocing a mistake :)
In general, when debugging units, it is often helpful to output to the console. Use of auto for intermediate values is also your friend... For example, here's what I did to figure out your problem:
thanks a lot, especially for the `auto` hint, which I totally forgot.
Steven - since you implemented the constants.hpp header, I'm a little reluctant to rummage through it. Could you please consider
1) adding support for the pow<> and root<> operations? 2) deprecating constant.value_type and constant.value() in favor of constant.quantity_type and constant.quantity() or constant.mean_value() or constant.mean() or something?
Also, can you remind me why we have "constant" and "physical_constant" structs? They look identical to me...
I'm looking forward to those improvements too :)
Janek,
I have attached headers implementing the various prefixed short cuts for the meter and joule; these two should be sufficient to extend to the rest of the SI unit system.
umm.. did you forget to attach the attachment? :)
What remains to be done is to replicate scaled_meter.hpp/scaled_length.hpp for the remaining base units in the <boost/units/base_units/si> directory and to replicate scaled_energy.hpp for all the remaining named SI units in the <boost/units/systems/si> directory.
ok. good. Do you need a test program, like then one below, for all those generated files?
Here's my test program:
#include <iostream>
#include <boost/units/io.hpp> #include <boost/units/systems/si/length.hpp> #include <boost/units/systems/si/energy.hpp>
#include "scaled_length.hpp"
#include "scaled_energy.hpp"
using namespace boost::units; using namespace boost::units::si;
int main() { std::cout << 1.0*nm << "\t" << 1.5*mJ << std::endl;
quantity<length> q1(1.0*nm); quantity<energy> q2(1.5*mJ);
std::cout << q1 << "\t" << q2 << std::endl;
auto q3(1.0*nm); auto q4(1.5*mJ);
std::cout << q3 << "\t" << q4 << std::endl;
return 0; }
and output :
1 nm 1.5 mJ 1e-09 m 0.0015 m^2 kg s^-2 1 nm 1.5 mJ
Note: if you assign these scaled quantities to unscaled quantities, the scaling information will be lost (second output line)...
for now this is not a serious problem. Maybe later when from functionality we will come to aesthetics of usage... :) best regards, and thanks a lot for your help! :) -- Janek Kozicki http://janek.kozicki.pl/ |