def subtract( self, time ):
if isinstance( time, RPNMeasurement ):
kneg = RPNMeasurement( fneg( time.getValue( ) ), time.getUnits( ) )
return self.add( kneg )
elif isinstance( time, RPNDateTime ):
if self > time:
delta = self - time
factor = 1
else:
delta = time - self
factor = -1
if delta.days != 0:
result = RPNMeasurement( delta.days * factor, 'day' )
result = result.add( RPNMeasurement( delta.seconds * factor, 'second' ) )
result = result.add( RPNMeasurement( delta.microseconds * factor, 'microsecond' ) )
elif delta.seconds != 0:
result = RPNMeasurement( delta.seconds * factor, 'second' )
result = result.add( RPNMeasurement( delta.microseconds * factor, 'microsecond' ) )
else:
result = RPNMeasurement( delta.microseconds * factor, 'microsecond' )
return result
else:
raise ValueError( 'incompatible type for subtracting from an absolute time' )
