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      The UFCS stuff that lets you write 100.kpa for kpa(100) is wild, I haven’t really seen it before in other languages, and it seems like it’d be great for exactly this use case.

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        Different, but F# has units of measure. Seems wonderful to be honest.

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          Those are clean as heck. The thoroughness and how they combine with the type system is really appealing.

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          Seems like something similar is possible in Ada too. (That web page takes a while to get to examples; search for Examples: to see a few.)

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            You can do a lot of it with C++ too (see std::chrono::duration for an example, including the ability to write things like 10ms in C++14). It’s a little bit clunky though. Derived units (e.g. m/s once you’ve defined m and s) are much harder: you can do it, but not automatically and you end up needing to define explicit conversion templates.

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          Yeah, it takes a bit of user code to make that happen in D, but it more-or-less can be done. see https://code.dlang.org/packages/quantities for an example

          Basically it creates a new subtype for each unit then the operator overloads do various combinations. So like 1.km / 1.sec will return a new km_per_sec unit which can be aliased to nicer names and compared etc. The .km there is a UFCS constructor call.

          Since you can do compile time evaluation of normal functions and pass string literals to them, you can do a bunch of the internal stuff with string processing to make it part of the type and whatnot.

          tbh though I never use these things in practice. Maybe I should it just never seems worth the hassle.

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        The Nim language also has UFCS, and I was not sure if I can write 100.foobar so I just tried, and yes I can:

        $ cat exp_units.nim
        proc km(i: int): int = 1000*i
        echo 5.km
        $ nim c -r --verbosity:0 exp_units.nim
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        Rails has 12.hours and so forth.

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          Doesn’t it do that by adding methods to the integer class (or however Ruby phrases it)? That’s similar, but not quite the same thing.

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            Yep. They aren’t quite units of measure, either; they just convert to a Duration (or whatever). You can of course combine 12.hours and 12.days because they’re of the same measure.