On Tue, Mar 11, 2014 at 11:30:44AM -0500, Tom Hawkins wrote:
Hi,
I just uploaded a handy library for managing engineering units. It provides a Num type that allows you to mix units into calculations. It also converts between units automatically and will error out if you try to mix values with inconsistent units.
Here's an example that computes the horsepower of a hydraulic pump (power = pressure * flow):
flow = 20 * gpm -- Gallons per minute. pressure = 3000 * psi -- Pounds per square inch. power = pressure * flow
powerHP = value power hp -- Get the value in horsepower. powerKW = value power kw -- Get the value in Kilowatts.
If you don't see your units in the library, it's easy to add new ones:
mm :: Value mm = 0.001 * m
Hi Tom, 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? 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 :) thanks, iustin