Static checking of units in Servo

https://blog.mozilla.org/research/2014/06/23/static-checking-of-units-in-servo/

by mbrubeck • 12 years ago

121 25 12 years ago

blog.mozilla.org

Furthermore, the units are used only at compile time. At run time, a Length<Inch, f32> value is stored in memory as just a single f32 floating point value, with no additional data. The units are “phantom types” that are never instantiated and have no run-time behavior.

I love that you get all of this safety with zero runtime cost.

dllthomas3• 12 years ago

This is the difference between types and tags (sometimes they're conflated).

illumen• 12 years ago

This code is buggy because they are using floats internally. A 32bit float can not represent the exact measurements specified.

This is a perfect example of why just statically type checking your code does not make it correct.

haberman2• 12 years ago

Every time I read about Rust I have to fight the urge to drop everything and just chase it. So much awesome going on over there.

coolsunglasses5• 12 years ago

We've been using stuff like phantom types in Haskell for years, where have you been?

http://www.haskell.org/haskellwiki/Phantom_type

wmf• 12 years ago

Being scared away by laziness, monads, and people generally talking like math geniuses, I guess.

haberman2• 12 years ago

I have mad respect for Haskell as an idea incubator, but it's not what I'd reach for as a systems programmer: https://news.ycombinator.com/item?id=7895890

Rust is awesome because it's bringing powerful ideas like this to a systems language.

coldtea3• 12 years ago

We've been using stuff like phantom types in Haskell for years, where have you been?

Lusting over a language that borrows its syntax from the Algol we all love and doesn't require a degree in Type Theory?

Oh, and without laziness, and with speed and no-GC guarantees...

bjz_• 12 years ago

I think he was making a more general statement than just in regards to the article. Being able to use a subset of the awesomeness of Haskell in a systems language is very refreshing.

DCKing• 12 years ago

Not really a great reply as 'phantom types' are possible in the majority (all?) of typed languages with generics. Even C++ has them - that is mentioned in the article.

What I think the OP was expressing is that the various articles written on people writing great code in Rust inspires people to work with it. Admittedly phantom types are not a distinguishing feature of Rust, but it still makes a nice read that people are elegantly solving real problems in the language.

mihai_ionic• 12 years ago

Boost has a neat library that does this and more: http://www.boost.org/doc/libs/release/libs/units/

orf• 12 years ago

But C++ is not cool so who cares.

Static checking of units in Servo

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