The case you claim requires drugs will happen eventually even if everybody is sober. I've seen it many times, and I doubt I'm the only one. Somebody is tired, o

The case you claim requires drugs will happen eventually even if everybody is sober. I've seen it many times, and I doubt I'm the only one. Somebody is tired, or they get the computer to perform some bulk change and get it wrong, or they are doing some rote transformation and they miss a case. If you want to do a bit better, a simple way of handling it is to provide a separate type that handles the abstract quantity (distance, money, etc. - you'd probably want to be cleverer about money if you deal with multiple currencies though), and ensure that values of that type can be converted to and from numbers only when the units are explicitly specified. So then you end up with functions that consume a distance looking something like this: void launch_rocket(Distance distance) { call_ancient_fortran_routine(get_miles_from_distance(distance)); } And functions that create distances looking something like this: launch_rocket(create_distance_from_km(100)); What you now can't do is create a value that's of one unit, and pass it to something that expects another unit - the issue doesn't really arise, as Distance values themselves don't have specific units. They are a black box that somehow encodes a distance, and you specify the units used explicitly when initializing and you specify the units desired explicitly if retriving an actual number. (Turning a distance into a number would ideally be a rare case, though sometimes you'd need it. You'd provide maths functions for all operations required, so you'd hopefully rarely need the number for calculation purposes. For displaying in any UI, there'd be a function to convert it to a string that respects the user's locale and distance unit preferences. And so on.)