On Oct 7, 5:24 am, Bas <[EMAIL PROTECTED]> wrote: > On Oct 7, 8:36 am, Lawrence D'Oliveiro <[EMAIL PROTECTED] > > central.gen.new_zealand> wrote: > > In message <[EMAIL PROTECTED]>, Gabriel > > > Genellina wrote: > > > As an example, in the oil industry here in my country there is a mix of > > > measurement units in common usage. Depth is measured in meters, but pump > > > stroke in inches; loads in lbs but pressures in kg/cm². > > > Isn't the right way to handle that to attach dimensions to each number? > > What they taught me as a physics undergrad is to always convert random > units given as input to SI units as soon as possible, do all your > calculations internally in SI units and (only if really needed) > convert back to arbitrary units on output. (snip)
If you think it's a potential source of error, a lightweight version wouldn't be hard to implement. This one is absolute minimal, using strings for the units. Multiplication is harder, since you want 'foot pounds' == 'pound feet'. >>> class UnitScalar: ... def __init__( self, val, type ): ... self.val, self.type= val, type ... def __add__( self, other ): ... assert self.type== other.type, 'Must be same type' ... return self.__class__( self.val+ other.val, self.type ) ... def __repr__( self ): ... return '<UnitScalar %f %s>'% ( self.val, self.type ) ... >>> a, b= UnitScalar( 2, 'feet' ), UnitScalar( 3, 'feet' ) >>> a+ b <UnitScalar 5.000000 feet> >>> a, b= UnitScalar( 2, 'feet' ), UnitScalar( 3, 'inches' ) >>> a+ b Traceback (most recent call last): File "<stdin>", line 1, in <module> File "<stdin>", line 5, in __add__ AssertionError: Must be same type -- http://mail.python.org/mailman/listinfo/python-list
