On Tuesday, 4 March 2014 at 13:20:02 UTC, Nordlöw wrote:
Thanks! I think David Nadlingers' is more elaborate (scaled and
affine units) and less prone to rounding errors. I haven't used
it yet. Mine is more basic but has a parsing system that I use
to
So you cannot defined things lika kPa from Pa in compile-time?
enum kPa = kilo(pascal);
which is equivalent to
enum kPa = 1000 * pascal;
Note that my module defines no real unit type, just quantities: a
unit is only a special quantity with a value of 1 and a set of
dimensions (a "base unit" in the sense of the SI). I think it
better fits what physical units really are. kPa would then be a
quantity that stores 1000 and a set of dimensions corresponding
to a pressure.
If you declare:
auto p = 101.3 * kPa;
p stores a value that is 101.3 * 1000 internally, not 101.3. With
David's library, I think you can declare kilopascal as a scaled
unit derived from pascal, and then a quantity in kilopascal would
actually store 101.3. The result is globally the same, but in
fact the representations of the numeric values would be a bit
different, and so would the rounding errors, when using floating
point types.
define units quickly at compile-time
Can't David's package also quickly define in compile-time?
I think it can.
Have you thought about merging your effort vid Davids and
propose it to Phobos? This issue has stale for quite some time
know.
I just think that David's package could have been proposed for
Phobos a long time ago. I don't know what has stopped it then. I
developed mine afterwards, not being aware of David's one.
I would like to have support add support for geometric units
like angles, coordinate systems, etc. Have you thought about
integrating these with your module?
My package is extendable. The SI module is just a predefined set
of common quantities and prefixes. You can use your own. Some
angle units are defined in quantites.si. I am not sure of what
you call a coordinate systems in this respect.
--
Nicolas
