I kind of feel like "untyped" is a term that doesn't really have a proper definition right now. As far as I can tell when people say "untyped" they usually mean it as a synonym for whatever they consider "dynamically typed" to mean (which also seems to vary a bit from person to person, haha). Sometimes people say assembly is untyped exactly for this reason, but you could also consider it to have one type "bits" and all of the operations just do things on bits (although, arguably different sized registers have different types). Similarly, people sometimes consider "dynamically typed languages" to just be "unityped" (maybe monotyped is more easily distinguished from untyped, haha) languages at their core, and if you squint you can just think of the dynamic type checks as a kind of pattern matching on a giant sum type.

In some sense values always have types because you could always classify them into types externally, and you could even consider a value to be a member of multiple types (often programming languages with type systems don't allow this and force unique types for every value). Because you could always classify values under a type it feels kind of weird to refer to languages as being "untyped", but it's also kind of weird to refer to a language as "typed" when there isn't really any meaningful typing information and there's no type system checking the "types" of values. Types sort of always exist, but also sort of only exist when you actually make the distinctions and have something that you call a "type system"... In some sense the distinction between static and dynamic typing is sort of an arbitrary implementation detail too (though, of course, it has impacts on the experience of programming, and the language design makes a bit of a difference in terms of what's decidable :) (and obviously the type system can determine what programs you consider to be "valid")... But you can absolutely have a mix of static type checking and dynamic typing, for instance... It's all a little more wishy washy than people tend to think in my opinion).

[–] [email protected] 3 points 10 months ago (1 children)

Well like asembly has "int types" and "float types" as there's specific instructions for those operations but those instructions don't actually care if the bits are for a float or an int. Types in a language are used to restrict the valid operations. In a statically typed language you cannot call cat.bark() or dog.meow() because the property's of the type, what things you can do with it are known before the program runs. In a dynamically typed language such as Python cat.bark() might or might not be valid so it has to check at runtime for a method throwing an error if it doesn't exist.

Static/Dynamic typing is a difference of when. Java has static typing but you can also just pass raw Objects around and cast when needed. It even throws a runtime exception similar to how Python or JavaScript would fail. However Java is of course ultimately statically typed everything just shares a common parent class and has types at runtime which allows for some some psudo dynamic behavior

[–] [email protected] 3 points 10 months ago

There’s operations that treat bits like floats and operations that treat them like various kinds of ints, but the meaning of bits is in the eye of the beholder. There’s even good examples of mixing and matching integer and floating point operations to clever effect, like with the infamous fast inverse square root. I feel like people often think mathematical objects mean something beyond what they are, when often math is kind of just math and it is what it is (if that makes sense… it’s kind of like anthropomorphizing mathematical objects and viewing them through a specific lens, as opposed to just seeing them as the set of axioms that they are). That’s kind of how I feel with this stuff. You can treat the bits however you want and it’s not like integer operations and bitwise operations have no meaning on supposedly floating point values, they do something (and mixing these different types of operations can even do useful things!), it just might not be the normal arithmetic operations you expect when you interpret the number as a float (and enjoy your accidental NaNs or whatever :P).

The difference of static and dynamic typing being when you perform the type checking is partially why I consider it to be a somewhat arbitrary distinction for a language (obviously decidable static type checking is limited, though), and projects like typescript have shown that you can successfully bolt on a static type system onto a dynamic language to provide type checking on specific parts of a program just fine. But obviously this changes what you consider to be a valid program at compile time, though maybe not what you consider to be a valid program overall if you consider programs with dynamic type errors to be invalid too (which there’s certainly precedence for… C programs are arguably only real C programs when they’re well-defined, but detecting UB is undecidable).