Like many good posts, this one got me thinking, and elicited a visceral reaction. The idea of traits as types is potentially interesting from a pedagogical per

Like many good posts, this one got me thinking, and elicited a visceral reaction. The idea of traits as types is potentially interesting from a pedagogical perspective, since it gives us another way of thinking about things. But whether it is simply analogous or is in fact homologous is the key question: If simply analogous, then we need to understand the limit of the analogy, where it works, where it fails. If homologous, then we have a powerful tool to draw upon, much like how mathematicians can switch analytic techniques equivalent over whatever category they are working with, or how physicists change coordinate systems to make the math and understanding easier for particular types of motion. I tend to think it is simply an analogy, but I don't yet know where its limits lie. > Really the only difference is that we manually convert from Friend to Display in Gleam, where Rust already knows how to use Friend as a Display.... Instead of a trait, just make a type that implements the generic behavior you want, and then write a function to convert your data-type into your trait-type. Aaaand here's where my gut twists. Why? Why would you do that? Why would you ever do "instead of... -> just" where the compiler will do it for you? Twice in that quote the author espouses writing more code because reasons, and, honestly, I don't think the reason is any better than "Gleam doesn't haven't traits and we're all OK with doing the extra work". That's fine. If that's how someone wants to work, and if their code works for them and is as maintainable as they need it to be, great! I cannot gainsay that. And I'll note that for someone who hasn't yet grokked generics and traits, the Gleam code may be more readable, because things are more spelled out. Sort of reminds me of my early Javascript, before I got comfortable with promises, composition, lambdas, and a few other things: Very readable blocks of code, often many lines long, that I would now replace with a single line. But once one understands traits and constraints, one can write very powerful, and, thanks to how Rust works, safe code that other (oh, I do have to use that term? oh, ok) Rustaceans will grok quickly, code that will likely also be performant. If I can save myself time and screen space AND make it clear to others what's happening AND make it safe and performant, I'm in. (I'll just remember to add comments as to why this is a single line and why that isn't.) (EDITS: Typos)