On August 22, 2014 4:08:34 AM EDT, Curdeius Curdeius wrote:

I was wondering if there is any interest in adding User-Defined Literals (UDLs) to Boost.Units.

IMO, it could simplify some code and improve code readability in some cases. For example instead of writing (it's a somehow artificial example) 5.34 * si::milli * si::kilogram; 1234 * si::kilogram; one would write 5.34_g; 1234_kg;

That would be much more readable, so the idea has merit. Usability, compile-time overhead, diagnostics, etc. would be factors in evaluating the result. ___ Rob (Sent from my portable computation engine)

It might be nice to support non-abbreviated varations: _milligram, _kiloton, _megabyte, etc. As an aside, there is a "derived" unit for just grams defined in there somewhere, maybe as part of the CGS subsystem? ----- Original Message -----

Hi all,

I was wondering if there is any interest in adding User-Defined Literals (UDLs) to Boost.Units.

IMO, it could simplify some code and improve code readability in some cases. For example instead of writing (it's a somehow artificial example) 5.34 * si::milli * si::kilogram; 1234 * si::kilogram; one would write 5.34_g; 1234_kg;

I propose to add this feature for compatible compilers (where BOOST_NO_CXX11_USER_DEFINED_LITERALS is not defined). The user would have to pull corresponding namespace (let's call it `udl`) to use it, for example using namespace boost::units::systems::si::udl; // bring _kg, _km, ... into scope

What are your feelings about it?

In the first place, I would go for `operator ""` taking as arguments `unsigned long long` and `long double`. Later, one could think about the one taking a `const char *` argument which would provide a quantity with an underlying type of arbitrary precision (like boost::multiprecision::cpp_int).

Regards,

Marek Kurdej -- Ph.D. candidate

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