What
It’s making fun of dynamic languages because rather than letting the compiler prove theorems about statically typed code, they… don’t.
Dynamic languages were invented by runtime error companies to sell more runtime errors.
Turns out getting working code is a lot cheaper and more useful than formally proven code.
And a lot more bug prone. I’m just explaining the OP because people didn’t get it. I’m not saying dynamic languages are bad. I’m saying they have different trade-offs.
And maintainable code is even cheaper and more useful than that in the long run.
Cheaper? Yes, I guess so, depending on how you measure cost. More useful? Absolutely disagree.
I may just be an old country lawyer PHP developer… but don’t most dynamic languages also support static type checking and general analysis at this point?
Yes but no. Modern PHP lets you put types in function signatures and it will then attempt to convert your inputs to those types at runtime.
JS/TS and Python don’t do this. They have optional type annotations that’s treated as syntactic sugar. You can use static checkers against this but if you get an error like “expected string got int” you can still run the code. It won’t behave any differently because you have annotations.
Yes if you use type annotations. Languages like Python and Typescript end up resorting to “Any” types a lot of the time, which breaks any kind of theorem proving you might have otherwise benefited from.
Though even statically-typed languages can need to check types sometimes; parsing runtime data for instance. I can see how you’d do that with pure statics, but it’d just be shifting the work (e.g. if token == QUOTE: proc.call(read_str(bytes, len))). It’d be cool to see a counter example that isn’t unreadable gibberish, however.
I need an explainer on this one
This is referencing Philip Wadler’s 1989 paper “Theorems for Free”, which is fairly well known in the Haskell community: https://home.ttic.edu/~dreyer/course/papers/wadler.pdf
🎵 Millions of theorems,
Theorems for free.
Millions of theorems,
Theorems for me, look out! 🎵
I’m sorry, I’m only a novice Python guy. Know enough to get two RESTful APIs to talk to each other and do some network automation or rudimentary Ansible plugins.
What’s wrong with if isinstance(x, str):?
Apparently, “Theorems for free!” is a paper that talks about an extensive ability to reason about parts of programs, if you follow some rather basic rules.
However, lots of popular programming languages throw this ability out the window, because they do not want to enforce those basic rules.
Most languages, for example, allow for rather uncontrolled side effects and to be able to reason as a programmer, you have to make the assumption that no one else abused side effects.
The instanceof is rather referring to dynamic typing, though, as e.g. employed by Python and JS, which makes it difficult to make any assumptions at all.
So, in statically typed languages, when you’re implementing a function, you can declare that a given parameter is a number or a string etc. and the compiler will enforce that for you. In dynamically typed languages, you have to assume that anyone calling your function is using it correctly, which is a difficult assumption to make after a refactoring in a larger codebase.
All in all, such different levels of rigorosity can be fine, but the larger your codebase grows, the more you do want such rules to be enforced, so you can just ignore the rest of the codebase.
