units

There 100% are unit systems implemented with types. (One example: https://github.com/goldfirere/units/tree/master/units) Structural types does not preclude having some names that prevent mix-ups. Haskell’s `data` keyword doesn’t let you confuse structurally-identical things. > If someone encodes "RGBColor" and "LinearRGBColor", both structs with 3 floats, your type system wouldn't provide any errors if a LinearRGB color is passed into an RGB calculation. It 100% would, unless you were silly enough to use a bare tuple to do it. Again, defining a type with `data` in Haskell wouldn’t get confused.

It seems to me that Haskell would be a great language for such a thing, ensuring correctness at compile time through the type system, e.g. using the units package https://hackage.haskell.org/package/units https://github.com/goldfirere/units/tree/master/units It even has nice features like: "The laws of nature have dimensions, and they hold true regardless of the units used. For example, the gravitational force between two bodies is (gravitational constant) * (mass 1) * (mass 2) / (distance between body 1 and 2)^2, regardless of whether the distance is given in meters or feet or centimeters. In other words, every law of nature is unit-polymorphic." "The units package supports unit-polymorphic programs ..." If on the other hand you just want a small calculator with units (which actually does also come with a library), there's qalculate ( ht

> double kilometerToMiles(double km) { return km / 1.6 } But what if you could have `miles kilometersToMiles(kilometers km)`? Under the hood its the same old doubles but you would be able to catch errors such as the one that caused Surveyor failure [1]. e.g. Haskell has units[2] and dimensional[3] that allow you to do exactly that [1] https://en.wikipedia.org/wiki/Mars_Climate_Orbiter#Cause_of_... [2] https://github.com/goldfirere/units [3] https://github.com/bjornbm/dimensional

There are several options for physical units of that sort in Haskell: https://wiki.haskell.org/Physical_units. I remember being fairly satisfied with unittyped: https://bitbucket.org/xnyhps/haskell-unittyped/. Though, enabled by GHC 7.8, units may now be nicer: https://github.com/goldfirere/units