units_ideas.txt

units:

_unitClassDict = {} # stores unit types that have been created
_valueClassDict = {} # stores types inheriting from numeric type _and_ unit type

def makeQuantity(value, unit=None):
	if isinstance(unit, basestring):
		lookup in dictionary of units
	if isinstance(value, PhysicalUnit):
		return value
	# create a new class which inherits from two classes,
	# the numeric class of the value, and the unit class
	cls = type(name, (ValueWithUnits, type(value)), {'__slots__': []})
	# store this

options:
    has-a value, has-a unit (Scientific Python approach)
    is-a value, has-a unit
    is-a value, is-a thingWithUnits, has-a unit
	is-a value, is-a thingWithUnits >> subclass with units stored in class *

+ we can use isinstance to determine what the PQs are.
+ no extra storage on instances
+ easy to do unit operations

- multiple inheritance
- how do we get at the unit itself? (inst.unit)
- new units are classes...ick!


makeValue(5, 'm')

U(5, 'm')

5 * U['m']