This can unleash so much hate mail, but here it goes, my inbox is ready!
Are dynamic languages just a temporary workaround? I’m not sure! I’m switching between the two types of languages all the time: Java, Python, C#, JavaScript. I’ll try to make the long story short.
Statically typed languages, like Java and C#, are nice because when you do
blah.bleh()
you know that blah’s class has a bleh method, at compile time. But better than that, when you typed “blah.” you get a list of methods, and you already know whether there’s a bleh method or not, and if you typed bleh and it doesn’t exist, the IDE lets you know, no need to wait for the compiler. Also you can do very deterministic refactoring, renaming all “bleh” for “bluh” for example.
Statically typed languages are not nice because they are very verbose and require a lot of boilerplate (if you’ve used Haskell, just bear with me for now please), so you end up with things like:
List[Car] cars = new List[Cars]();
foreach (Car car in cars) {
car.Crash();
}
How many “cars” do you read there? And that’s a nice example. There are worse. So come dynamically typed languages and you can write:
cars = []
for car in cars:
car.crash()
You have less cars, and less (no) lists. That means you are more productive. You start chunking out code faster without having to stop and think “What type of object will this or that method return?”. But crash() can crash your application instead of just the car because you can’t know if it exists until run-time. That might be OK or not, testing and whatnot.
Then comes C# 3.0 where you can do:
var cars = new List[Car]();
foreach (var car in cars) {
car.crash();
}
And you can see that syntactically it got closer to Python, which is what gives you the productivity. Don’t know the type? type “var”. But semantically, it’s still statically typed, like the previous statically typed example. You know that car is going to be of some class that has a crash method. You can actually know car’s class at compile time, no need to run it.
That’s called type inference. You don’t have to specify the type where the compiler is capable of inferring it for you. C# type inference system is still very limited (but better than Java’s). Let’s see an example in another language
cars = [] map crash cars
That means, create a list called cars, call the function crash on each car. Would you say that that is a statically typed language? or a dynamic one? I’d say it is dynamic, but it is static. Very static. It’s Haskell. Haskell’s compiler will infer all the types for you. It’s amazing, you’ll write code as robust as with C#, but as terse as Python’s (Monads will then kill your productivity, but that’s another story).
In Python 3 you can define types for arguments. They are mostly useless, but it’s an interesting direction. I think the best it can do is that when a program crashes it’ll tell you: “function blah expected an int, but got a float, not sure if that was the problem, but you might want to look into that”.
Now, my question is, are dynamically typed languages just a temporary workaround? As our compilers get better, our computers faster, will statically typed languages keep giving us as many or more reassurances about our code and utilities while at the same time they become as simple and terse as dynamically typed languages? Or will dynamically typed languages start to gain types and over time be more static without the programmers that use them ever noticing?
My question is, will we in the future, 50 or 100 years, look back and said “Dynamically typed languages where a temporary workaround to statically languages being painful to use when human beings and their toy computers were so primitive?” in the same way we can say today that “non-lexical scope was a limitation we had and have due to the limitations of computer hardware 30 years ago”.
Reviewed by Daniel Magliola. Thank you!
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