[units] easier scaled units generation

4 May 2010

      scaled units are a great feature of boost.units, however it seems
complicated to (explicitly) create  variables in such units. This is
the way I found to create a variable that stores a quantity like
GigaPascals:

 using boost::units;
 typedef make_scaled_unit
...
...
::type gpa_unit;
 gpa_unit GPa;
 quantity p(1.*GPa); //or p(1.*si::giga*si::pascal);
the question is, is there a simpler way of doing this? for example,
just

 quantitysi::pressure > p = ...; //values are converted/stored
in giga pascals.

I could add some "metafunction":

template<class Unit> giga{
 typedef make_scaled_unit >
...
::type unit;
};
and use it like
 quantitysi::pressure::unit> p;

and even specialize for femto, atto, mega, kile, etc. I this already
implemented in some other way?

In this way if I had implemented an electronvolt unit I could have
megaelectronvolt for free

 quantity::unit> energy = ...;

Thank you,
Alfredo

alfC

Matthias Schabel

alfC

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