4 ms·

I don't see how "typed/untyped" is a meaningful distinction if you consider "dynamic types" to be types. If the only observable effect of the typechecker in a d

by gue5t 10y ago

I don't see how "typed/untyped" is a meaningful distinction if you consider "dynamic types" to be types. If the only observable effect of the typechecker in a dynamically-typed language is a runtime error, how do we distinguish an arbitrary source of runtime errors (e.g. "throw" or "error" statements) from a dynamic typechecker? Obviously it isn't the presence of the word "type" in error messages, but what is it? In the presence of the metaprogramming you describe, we can't say it's down to whether checks are inserted automatically either, since non-type dynamic checks may also be inserted pervasively and automatically with metaprogramming. If Lisp is typed, what's an "untyped" language? One in which the user hasn't done metaprogramming to insert runtime checks? Or is the distinction just about whether it's the end programmer or the language implementor who does the metaprogramming? None of these seem like very useful distinctions. If it's lispy to actually do a separate typechecking pass, please forgive my ignorance.

zem 10y ago
i'd say an untyped (well, weakly typed; every language has some notion of types) language was one like C where you can construct a value of some type, and then treat the block of memory in which the physical representation of that value is stored as some other type. that said, eric lippert has a good blog post on [defining our terms more precisely before even asking the question](https://ericlippert.com/2012/10/15/is-c-a-strongly-typed-or-a-weakly-typed-language/ https://ericlippert.com/2012/10/15/is-c-a-strongly-typed-or-...)
- telotortium 10y ago
  There are in fact typeless languages that are neither statically nor dynamically typed, although they aren't particularly relevant nowadays -- BCPL, Forth, and assembly, among others. These languages have only words that hold integer values, with different operators treating the words as an integer, pointer, etc. Those who claim that only static types are worthy of the name "type" would probably consider both dynamically typed and typeless languages to be equally untyped -- dynamically typed languages just support richer semantics on their values, such as storing a "tag" (i.e., dynamic type) in each value.
tmerr 10y ago
Imagine a language where you work with blobs of data and have no restrictions on the operations between them. Like assembly languages. You can add a char* and float and the compiler won't complain. I would call that untyped. A typed language restricts the operations you can perform on blobs of data by classifying them. A user could build a more restrictive type system on top of an already typed language. The distinction between a type system and an arbitrary source of runtime errors is that a type system has the properties i described earlier, and also it has the cohesion you would expect from it being a "system". A smattering of if statements wouldn't qualify. That's one way to look at it I guess. Everyone has their own working definitions so I still it's still reasonable if you consider dynamically typed languages to be untyped.

by gue5t 10y ago

zem 10y ago

i'd say an untyped (well, weakly typed; every language has some notion of types) language was one like C where you can construct a value of some type, and then treat the block of memory in which the physical representation of that value is stored as some other type. that said, eric lippert has a good blog post on [defining our terms more precisely before even asking the question](https://ericlippert.com/2012/10/15/is-c-a-strongly-typed-or-a-weakly-typed-language/ https://ericlippert.com/2012/10/15/is-c-a-strongly-typed-or-...)

telotortium 10y ago
There are in fact typeless languages that are neither statically nor dynamically typed, although they aren't particularly relevant nowadays -- BCPL, Forth, and assembly, among others. These languages have only words that hold integer values, with different operators treating the words as an integer, pointer, etc. Those who claim that only static types are worthy of the name "type" would probably consider both dynamically typed and typeless languages to be equally untyped -- dynamically typed languages just support richer semantics on their values, such as storing a "tag" (i.e., dynamic type) in each value.

tmerr 10y ago

Imagine a language where you work with blobs of data and have no restrictions on the operations between them. Like assembly languages. You can add a char* and float and the compiler won't complain. I would call that untyped. A typed language restricts the operations you can perform on blobs of data by classifying them. A user could build a more restrictive type system on top of an already typed language. The distinction between a type system and an arbitrary source of runtime errors is that a type system has the properties i described earlier, and also it has the cohesion you would expect from it being a "system". A smattering of if statements wouldn't qualify. That's one way to look at it I guess. Everyone has their own working definitions so I still it's still reasonable if you consider dynamically typed languages to be untyped.