That helps quite a lot, although for several, it's more programming-by-name than programming-by-semantics. I'd like to be able to say the end angle has to be l

That helps quite a lot, although for several, it's more programming-by-name than programming-by-semantics. I'd like to be able to say the end angle has to be less than the start angle, that the unit has to be radians (AKA unit-less :), the unit of radius & that negative values are sensical, and so forth; and have all these properties checked by a compiler. Which I can do in some modern languages, surprisingly. :)