Discussion
Type systems are leaky abstractions: the case of Map.take!/2
mcphage: > Unfortunately, this decision completely defeats the purpose of adding a function similar to Map.take!, as the goal of the function is to return a map where we are certain the given keys exist!I mean, if you define a function calling Map.take! that returns one of two possible set of keys based on a random number, I’m not sure it’s actually possible to get a map where you’re certain what keys exist.
travisgriggs: I think his point was any logic branch which branches on any state injected by the world outside of the compilation scope.
travisgriggs: “Every institution perishes by an excess of its own first principle.” - Lord ActonFor the reasons explored in the post, I prefer my type systems optional. It has been my experience and observation that typing in languages follow an 90:10 rule. You get 90% of the gains for 10% of the effort. And the remaining 10% for 9x the effort.I’m rather happy with the way Python allows me to do the easy ones and/or pick the hotspots.I’ve worked in exhaustively typed languages, and while it gives a sense of safety, it’s literally exhausting. And, anecdotally, I feel I dealt with more zero divides, subscript woops, and other runtime validation errors than I had in less typed languages.Not that it matters. Soon, we’ll use semantically vague human language, to prompt, cajole, nudge LLM agents to produce programs that are (lossy) statistical approximations of what might be correct programs.
logicprog: This seems like a really easy problem to avoid by simply having a better type system and knowing how to use it. namely just have the take! function return an optional map where it returns Some(map) if the map has the expected keys and None if the map it would have returned in the non-asserting version wouldn't have been valid (I.e, wouldn't have had the expected keys). Then if you really want to assert on this, you just use .unwrap or .expect.
foxes: So if we pretend a list is a function from an index to an entry for the moment ``` Enum.take(list , 2) ``` Is more like ``` Enum.take(list, [1,2]) ``` So if you apply that to a list of length 1 or zero, you just get either list[1], or []The difference is that Enum is maybe a total function - the domain of the function is always well defined, while Map take is trying to be dressed up as a total function but its really something thats only partial.So the type system needs a way to describe a map that has "at least these keys" a bit like the enum case. So that requires some polymorphism.
HauntingPin: I've worked with both Java and Python extensively. Python's type system is far more exhausting, tbh. You have to think about types in both languages, but at least in Java, the compiler and static analysis can tell you if there are type-related issues. In Python, runtime errors. Anything larger in Python becomes a nightmare to work with because you basically never know for sure what's being passed into a function without excessive type checking and testing.
kace91: Every time I've interacted with optional type systems, it feels like I'm driving in a road where only 50% of the drivers follow the rules.Meaning, it's just as hard as no one following rules, but on top of that I get blindsided by expectations of security.
