4 ms·

> No tool can, by itself, overcome your ignorance of its necessity. A type system that understands units of measurement can help: https://learn.microsoft.com/

by nequo 3y ago

> No tool can, by itself, overcome your ignorance of its necessity. A type system that understands units of measurement can help: https://learn.microsoft.com/en-us/dotnet/fsharp/language-reference/units-of-measure https://learn.microsoft.com/en-us/dotnet/fsharp/language-ref...

klausa 3y ago
That still requires you to know about its existence. It's perfectly possible to write F# code without those and messing up units conversion.
- nequo 3y ago
  Someone on the team needs to know about it. That person needs to set up the API to expect properly typed inputs. Others can remain ignorant about units of measurement and the compiler will educate them. F# has this built in but it can be achieved with libraries in some other languages. For example, in Haskell with the dimensional package[1]: import Numeric.Units.Dimensional.Prelude import Numeric.Units.Dimensional.NonSI (mile) speedLimit :: Velocity Double speedLimit = 30 *~ (mile / hour) main :: IO () main = do let speed1 = 35 *~ (kilo meter / hour) let speed2 = 35 *~ (mile / hour) let speed3 = 35 print (speed1 <= speedLimit) print (speed2 <= speedLimit) print (speed3 <= speedLimit) GHC will give you an error because `speed3` is mistyped. [1] https://hackage.haskell.org/package/dimensional https://hackage.haskell.org/package/dimensional
  - midoridensha 3y ago
    You're not getting it. The Mars probe didn't crash because of bad unit conversion. It crashed because there were no units in the data!!! Go read about it yourself. NASA got some data from a contractor. The data had no units at all. The contractor assumed the data to be in some kind of US-standard units. NASA got these raw numbers and assumed they were in some kind of SI units. Having enforced units in your language isn't going to help in this situation at all. They weren't exchanging code, they were exchanging raw data, or more specifically, a table with a bunch of numbers on it. The people at NASA simply assumed some units (instead of calling the contractor and asking), and they would have done this in your scenario too.
    - nequo 3y ago
      In that case, you're right.
    - fbdab103 3y ago
      Notably, the NASA spec said the units were supposed to be in SI.

by nequo 3y ago

klausa 3y ago

That still requires you to know about its existence. It's perfectly possible to write F# code without those and messing up units conversion.

nequo 3y ago
Someone on the team needs to know about it. That person needs to set up the API to expect properly typed inputs. Others can remain ignorant about units of measurement and the compiler will educate them. F# has this built in but it can be achieved with libraries in some other languages. For example, in Haskell with the dimensional package[1]: import Numeric.Units.Dimensional.Prelude import Numeric.Units.Dimensional.NonSI (mile) speedLimit :: Velocity Double speedLimit = 30 *~ (mile / hour) main :: IO () main = do let speed1 = 35 *~ (kilo meter / hour) let speed2 = 35 *~ (mile / hour) let speed3 = 35 print (speed1 <= speedLimit) print (speed2 <= speedLimit) print (speed3 <= speedLimit) GHC will give you an error because `speed3` is mistyped. [1] https://hackage.haskell.org/package/dimensional https://hackage.haskell.org/package/dimensional
- midoridensha 3y ago
  You're not getting it. The Mars probe didn't crash because of bad unit conversion. It crashed because there were no units in the data!!! Go read about it yourself. NASA got some data from a contractor. The data had no units at all. The contractor assumed the data to be in some kind of US-standard units. NASA got these raw numbers and assumed they were in some kind of SI units. Having enforced units in your language isn't going to help in this situation at all. They weren't exchanging code, they were exchanging raw data, or more specifically, a table with a bunch of numbers on it. The people at NASA simply assumed some units (instead of calling the contractor and asking), and they would have done this in your scenario too.
  - nequo 3y ago
    In that case, you're right.
  - fbdab103 3y ago
    Notably, the NASA spec said the units were supposed to be in SI.