4 ms·

What you say sounds interesting but could you give an example of "think in contracts" compared to and example of "knowing the runtime state in your head". Pers

by collyw 6y ago

What you say sounds interesting but could you give an example of "think in contracts" compared to and example of "knowing the runtime state in your head". Personally I have never really seen the advantage of staticaly typed languages over say Python, but I do rely on the strict typing supplied by a database instead.

eyelidlessness 6y ago
What I mean is that static typing makes interface boundaries (modules, function parameters and return types, data structures) explicit, and those boundaries are enforced automatically. Those boundaries become a contract, where a provided interface and its call sites must agree on in order to be run. This is like a million little unit tests you get almost for free (obviously you have to write the types, but they're usually declarative and very expressive). But it also serves as documentation of how any part of your program's state is structured at any point. To the degree a type system is sound, and to the degree your types are appropriately detailed, you can be assured the documentation is correct and up to date as long as the program compiles. This allows you to eliminate the question of "what does this data look like?" when you're reading code, and focus more on things like whether the logic is implemented correctly. Since you mention it, I'll add that Python does have (optional, gradual) static typing, and a lot of work has gone into the type system in recent versions. It's worth spending a little time adding some static types in a project and seeing some of these benefits. When I last worked in Python, you had to run `mypy` to actually fail on static type errors, I don't know if this is still the case. But you could also use an IDE (like PyCharm, surely there are others) which will at least surface static type errors while you work.
- collyw 6y ago
  I have been using Python type hinting recently, but I don't find it such a big game changer. Maybe I am just used to writing code without it and it will become clearer if I use it more. Like I say I don't like having an untyped database, and the benefits there aren't things that are obvious straight away.
  - eyelidlessness 6y ago
    When I last worked in Python, I also didn't get much benefit, but I wasn't using either mypy or an IDE that warns on type errors. While obviously a different language, it wasn't until I worked with TypeScript in VSCode that I really came to appreciate static typing. And after a few years, I don't think I could go back to working without it.

by collyw 6y ago

eyelidlessness 6y ago

What I mean is that static typing makes interface boundaries (modules, function parameters and return types, data structures) explicit, and those boundaries are enforced automatically. Those boundaries become a contract, where a provided interface and its call sites must agree on in order to be run. This is like a million little unit tests you get almost for free (obviously you have to write the types, but they're usually declarative and very expressive). But it also serves as documentation of how any part of your program's state is structured at any point. To the degree a type system is sound, and to the degree your types are appropriately detailed, you can be assured the documentation is correct and up to date as long as the program compiles. This allows you to eliminate the question of "what does this data look like?" when you're reading code, and focus more on things like whether the logic is implemented correctly. Since you mention it, I'll add that Python does have (optional, gradual) static typing, and a lot of work has gone into the type system in recent versions. It's worth spending a little time adding some static types in a project and seeing some of these benefits. When I last worked in Python, you had to run `mypy` to actually fail on static type errors, I don't know if this is still the case. But you could also use an IDE (like PyCharm, surely there are others) which will at least surface static type errors while you work.

collyw 6y ago
I have been using Python type hinting recently, but I don't find it such a big game changer. Maybe I am just used to writing code without it and it will become clearer if I use it more. Like I say I don't like having an untyped database, and the benefits there aren't things that are obvious straight away.
- eyelidlessness 6y ago
  When I last worked in Python, I also didn't get much benefit, but I wasn't using either mypy or an IDE that warns on type errors. While obviously a different language, it wasn't until I worked with TypeScript in VSCode that I really came to appreciate static typing. And after a few years, I don't think I could go back to working without it.