Re:Strong typing, a hill I'm willing to die on
by nyssos on Friday October 06, 2023 @11:46PM
(#37798850)
> templating
Yes, running arbitrary code at compile-time can produce arbitrarily complicated results if you're not very very careful. This is not a type system issue: lisp macros are just as dangerous.
> abstract base classes
Again, nothing to do with types: your complaint is with Java-style OO. Which is garbage, but for historical Java-specific reasons. Using Java as your prototypical example of a typed language is like using PHP as your prototypical example of a dynamic language. There's no such thing as a feature good enough to rescue a bad language. That doesn't mean no feature of a bad language can ever be good.
> generics
Generics produce strictly simpler code than copy-pasting the same implementation over and over again. That's their entire purpose. A generic function isn't a way to give the same name to different pieces of code (the way that inheritance is, for instance), it's literally one function: `mapIntList` is `mapFloatList` is `mapStringList` is `mapIntListList`, all the way down to the compiler output. Unless you're doing some pretty serious performance optimization, giving them different implementations is a bug. And you wouldn't do so in a dynamic language either!
> non-trivial user defined types
These exist as part of your program structure whether you like them or not, the only question is whether they've been made explicit.
> Consider a simple program that adds 2 numbers: a & b together. In a dynamically typed language, this would be a + b. In a statically typed language, once you consider overflow and underflow, you will likely have a hundred lines of code.
Considering overflow and underflow in the static case but not the dynamic case is stacking the deck. Either you're using arbitrary-precision numbers or you're not.
Here's Haskell code for adding two numbers:
add :: Num x => x -> x -> x
add a b = a + b
If you don't want to worry about overflows, you use `Integer`s, which are arbitrary precision. If you're worried about performance, you use `Int`s, which are machine integers.
You can complain that this isn't "really" the addition code, since we're calling out to the `Num` instance, but the same applies to dynamic languages. Python's `a + b` is calling out to `__add__` in exactly the same way.
> This creeps up again in JSON parsing where the types really are defined at runtime.
They are not. The type of arbitrary JSON is (using Haskell again)
data JSON =
| JSONNull
| JSONBool Bool
| JSONNumber Double
| JSONString Text
| JSONArray [JSON]
| JSONObject (HashMap Text JSON)
(You don't have to use a hash map, of course: decoding the raw text stream to JSON is a separate step). You then check that it has the structure you expect by implementing a function `jsonToFoo :: JSON -> Either MyPreferredErrorType Foo`.
Yes, running arbitrary code at compile-time can produce arbitrarily complicated results if you're not very very careful. This is not a type system issue: lisp macros are just as dangerous.
> abstract base classes
Again, nothing to do with types: your complaint is with Java-style OO. Which is garbage, but for historical Java-specific reasons. Using Java as your prototypical example of a typed language is like using PHP as your prototypical example of a dynamic language. There's no such thing as a feature good enough to rescue a bad language. That doesn't mean no feature of a bad language can ever be good.
> generics
Generics produce strictly simpler code than copy-pasting the same implementation over and over again. That's their entire purpose. A generic function isn't a way to give the same name to different pieces of code (the way that inheritance is, for instance), it's literally one function: `mapIntList` is `mapFloatList` is `mapStringList` is `mapIntListList`, all the way down to the compiler output. Unless you're doing some pretty serious performance optimization, giving them different implementations is a bug. And you wouldn't do so in a dynamic language either!
> non-trivial user defined types
These exist as part of your program structure whether you like them or not, the only question is whether they've been made explicit.
> Consider a simple program that adds 2 numbers: a & b together. In a dynamically typed language, this would be a + b. In a statically typed language, once you consider overflow and underflow, you will likely have a hundred lines of code.
Considering overflow and underflow in the static case but not the dynamic case is stacking the deck. Either you're using arbitrary-precision numbers or you're not.
Here's Haskell code for adding two numbers:
If you don't want to worry about overflows, you use `Integer`s, which are arbitrary precision. If you're worried about performance, you use `Int`s, which are machine integers.You can complain that this isn't "really" the addition code, since we're calling out to the `Num` instance, but the same applies to dynamic languages. Python's `a + b` is calling out to `__add__` in exactly the same way.
> This creeps up again in JSON parsing where the types really are defined at runtime.
They are not. The type of arbitrary JSON is (using Haskell again)
(You don't have to use a hash map, of course: decoding the raw text stream to JSON is a separate step). You then check that it has the structure you expect by implementing a function `jsonToFoo :: JSON -> Either MyPreferredErrorType Foo`.