On Tue, Mar 11, 2014 at 4:03 PM, Iustin Pop wrote:

Looking at your documentation, I see a lot of sense behind implementing different units (Horsepower vs. Watts), but I'm not so sure about (for example) g/kg or m/cm/mm. These are just (SI) scaling factors, so should they be treated the same as individual units?

Depends on if the difference shows up to the user. I've been using a calculator/scripting language (Frink) for years that has this kind of facility, and while I know that they are just scaling factors, I still treat them as different types of units. That may be because I grew up using imperial units, and inches/feet/yards/miles don't allow for being treated that way.

For just the scaling factors, I released last year http://hackage.haskell.org/package/prefix-units, and I'm wondering if we couldn't somehow combine these two libraries. After all, "k" applies both to KG and KW :)

Yes, but "KV" is not _always_ a kilovolt. When used on an electrical motor, it's a measure of how many thousands of RPM you can expect the motor to turn when for each volt of power it's fed. I'm hoping to get around to desiging the power system for a multirotor this year, and will be interesetd to see how various tools deal with this issue.

Hello, There are many libraries mentioned here too: http://www.haskell.org/haskellwiki/Physical_units. I don't know of a good comparison of the various options for runtime and compile-time checked units. Regards, Adam On Tue, Mar 11, 2014 at 4:36 PM, Douglas McClean wrote:

You may also be interested in the various flavors of Björn Buckwalter's dimensional library.

On hackage it's dimensional-tf (for type families, and my preference) or dimensional (for multi-parameter type classes).

We are working on making a version that takes advantage of the new GHC DataKinds features to provide even more features, that's at https://github.com/bjornbm/dimensional-dk.

-Doug

On Tue, Mar 11, 2014 at 4:26 PM, Mike Meyer wrote:

...

On Tue, Mar 11, 2014 at 4:03 PM, Iustin Pop wrote:

...

Looking at your documentation, I see a lot of sense behind implementing different units (Horsepower vs. Watts), but I'm not so sure about (for example) g/kg or m/cm/mm. These are just (SI) scaling factors, so should they be treated the same as individual units?

Depends on if the difference shows up to the user. I've been using a calculator/scripting language (Frink) for years that has this kind of facility, and while I know that they are just scaling factors, I still treat them as different types of units. That may be because I grew up using imperial units, and inches/feet/yards/miles don't allow for being treated that way.

...

For just the scaling factors, I released last year http://hackage.haskell.org/package/prefix-units, and I'm wondering if we couldn't somehow combine these two libraries. After all, "k" applies both to KG and KW :)

Yes, but "KV" is not _always_ a kilovolt. When used on an electrical motor, it's a measure of how many thousands of RPM you can expect the motor to turn when for each volt of power it's fed. I'm hoping to get around to desiging the power system for a multirotor this year, and will be interesetd to see how various tools deal with this issue.

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