NORMAL BRAIN: Systems Hungarian may be silly, but Apps Hungarian has some merit
GALAXY BRAIN: Apps Hungarian is stupid and just duplicates the work of the type system
But yeah, zero cost compiler magic is the reason Rust is so good.
Is this correct? From the article, Apps Hungarian represents your intent for the var (the kind), not the type. Systems Hungarian represents the type (duplicative).
For example, see https://talks.golang.org/2012/goforc.slide#43.
https://fsharpforfunandprofit.com/posts/designing-with-types...
https://www.merriam-webster.com/words-at-play/what-does-crom...
(Edit: Add link)
I've tried using a unit system library in Rust, for audio programming. It was not worth it for me. I had to define types for clock cycles, audio sample durations, and amplitudes. Then cycles per second and samples per second were expressed as ratios. Then you need (cycle / second) to have type (cycles per second). The typenum-based error messages were dreadful. And also you sometimes need to use different base numeric types used to store these dimensioned quantities. And also write extra typecasts to box and unbox between unit-wrapped quantities and plain integers.
The correct way of doing Hungarian Notation, as demonstrated in this article, is to encode in the name of the variable what it does, not its type.
No compiler can know that a string variable is a "name" or a "password".
That said, I generally agree that conventional type systems are not (yet) capable of encoding all those informations to a type. I prefer a mix of actual types and coding conventions for the practical matter.
Java for example has to leave quite a lot of that information in names because there are no type aliases and final types exist.
type User_Id_Type is new String;
type User_Credential_Type is new String;
You can also add static predicates to ensure User_Id_Type doesn't contain spaces. You can also make the type 'opaque' and it won't be possible to convert to a String without a bespoke interface.
I'm not sure what's missing. I almost feel like it would be a great challenge :-)
It is much harder, if not impossible, if you have to describe a relation between two or more values of the same subtypes. For example, imagine that you already "know" certain indices never go off the boundary of given array but want to encode that information to types. Sure, there exists a Rust crate [1] that tracks a relation between indices and originating array via lifetime, but it is complicated.
I'm wondering if using type predicates or type invariants (+ proof for static verification, otherwise the check will mostly be at runtime) would help here.
Look up https://blog.adacore.com/spark-2014-rationale-type-predicate... if interested.
In pretty much any language supporting user-defined types and/or type aliases, types can be used for that information (with aliases, providing documentation the same as hungarian notation does; with real types, providing the possibility for enforced protection against accidental misuse.)
But the article doesn't actually use hungarian notation for that kind of thing, it uses it for traits that are not "what it does", but instead metadata analogous to Ruby's "taint". Which, again, is something easily encoded in typing, in a static language, either as a core feature of typing or via user-defined (possibly wrapper, depending on other features of the type system or general language semantics) types; type aliases, even, would work as well as hungarian notation, but using actual types lets you put guarantees in place rather than just providing documentation.
Type alias can also do that, but they can do so in a way where correctness can be statically enforced.
As an example, let’s say you have a Write function like in the article, but it only takes an HTMLString, which can’t implicitly be casted from String. Then, you can have Encode return an HTMLString, but take a String. Finally, you can use static analysis to only allow whitelisted functions to construct non-literal HTMLStrings (so anyone could do a literal of HTML, but every other usage would require encoding or whitelisting.)
This is a bit rudimentary of an example, but it is widely used in practice.
Here is a safe type used in Closure:
https://google.github.io/closure-library/api/goog.html.SafeH...
In Scala you have value class, that get replaced by the underlying type during compilation so there is no overhead.
https://ivanyu.me/blog/2014/12/14/value-classes-in-scala/
It may sounds a hassle but you only have to handle it at the interfaces (for example for a web app in the controller and data layer), in the rest of the code you just manipulate your value like any other type.
Using prefixes is a poor man's type system, a loose convention to be enforced by humans, while with types it would be a machine-readable and enforceable requirement.
type Password string type Name string
func SayHello(name Name) { fmt.Println("Hello %s",string(name)) }
func Login(password Password) bool { if bcrypt.magicstuff([]byte(password)){ return true } log.Println("error: wrong password: ", string(password)) return false }
Now the type system does know whether it's a name or a password, and will throw a compiler error if you try to use the wrong one in the wrong place.
edit: really HN, no code formatting options? :(