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Same here: having gone from C++ to JS+Python and back to Golang/Rust, I just can't imagine life without types. However, of all the not-static-typed language ec

• _bxg1 6y ago
  A pure functional style does help somewhat; things are more predictable and consistent, expressions can be evaluated inline to test them out, etc. And I think Clojure teams (Lisp teams in general, really) are already forced to be on the small side because of how flexible things can become with macros and such. You have to have a stronger shared headspace compared to, say, a Java project. So that also lends itself to being more dynamic-types-tolerant. Finally, that very flexibility (with macros, etc.) is only fully possible in the absence of static types. So there is a genuine tradeoff. Still, even with all of the above I'd rather have them than not have them.
• slifin 6y ago
  If you want something to let you know you've made a silly mistake like putting a string in a number function or missed an argument use clj-kondo it will catch those problems for you in the editor If you want to make a Person class or type I would recommend instead making your information model as a Datomic schema and have all your functions use associative destructuring with defaults values for missing data with function comments for good measure For dev I would recommend Datahike over Datomic initially
• lorddoig 6y ago
  It depends what you want to use types for, really. If your motivation for using types is provable correctness and you can grok Haskell (or better yet, Idris), then you should do that. If you want performant dispatch, Clojure can give you JVM-level perf through the use of protocols. If, however, you want input validation (in the sense that you can be sure that a function argument you've been given will allow you to do what you intend with it) then static typing isn't the only player in that game. In my experience (which I think resonates with RH and most Clojurists) is that for the vast majority of _information-driven_ systems, types are used as the latter. If you have a `Customer` class that gives you guarantees about the availability of, say, an `accountNumber` field, that is useful for correctness as you can be sure the information you need is there. However, if some future downstream coder wants to use your customer in the more general sense of being a human, then (s)he has to worry about sub/super/abstract-classing, may have to make upstream modifications to expose previously hidden data, and similar faffage. In Clojure the idiomatic solution to this problem is to "just use a map"; the real-world downside to this, however, is extremely weak contracts between functions. In this example, what `spec` allows you to do is strengthen those contracts by verifying that the data your function is provided is sufficient for your uses (as in the map contains all the keys you'll need with suitable data types in the fields) _without_ constraining what downstream consumers can also do with this data (extra map keys are ignored). These checks are only done at runtime and only when enabled, however writing a spec gives you (very-nearly-almost) free generative testing that will run your function a default of 1000 times with random data in the correct shape to make sure it doesn't blow up—this isn't a guarantee of correctness, but it does provide extremely high levels of confidence (most type systems are also not even close to guaranteeing correctness either, only compliance with the type system). Spec also gives you (for free) performant runtime coercion for use in actual real-world code. You get a lot of bang for your buck. `spec` is definitely not a type system, but it very capably fulfils a similar role in the kinds of programs Clojure was intended to be good at. It gives you all the flexibility and dynamism of Clojure with most of the confidence of static typing, without constraining either.
  • _bxg1 6y ago
    > by verifying that the data your function is provided is sufficient for your uses (as in the map contains all the keys you'll need with suitable data types in the fields) _without_ constraining what downstream consumers can also do with this data (extra map keys are ignored) This assumes a very class-oriented type system. Duck-typing and the like don't have the upstream ontology problems. My main desire from types is as an iteration assistant (with editor integration). Even if I wrote a function myself, I may not remember the exact order of arguments, or the exact name of that one property on the returned map. I want to a) be able to quickly peek and see what those things are - either by visiting the definition or, even better, via a pop-over in my editor - and b) have my editor tell me immediately if I did something dumb so I can correct it and keep moving. In a dynamic language, whenever I need to double-check the contract for some code, I can't just go look look at its type signature, I have to go read through it. I have to fully load that whole subtree of information into my brain (recursively to any functions it may itself call), when I'm really trying to focus my thoughts on something else. This can be a huge, needless drain on mental resources. Spec would help with this some, assuming the author follows a good convention of putting all of their assertions at the top of the function. But maybe those assertions are done inside conditionals, creating a more complex type. And maybe my editor doesn't know what to make of them (do any editors? genuinely curious). Etc. It just creates a bunch of little speedbumps to cognition that add up.
    • lorddoig 6y ago
      > In a dynamic language, whenever I need to double-check the contract for some code, I can't just go look look at its type signature, I have to go read through it. I have to fully load that whole subtree of information into my brain (recursively to any functions it may itself call), when I'm really trying to focus my thoughts on something else. This can be a huge, needless drain on mental resources. Yes, this is a headache, and certainly a problem that afflicts Clojure. Spec doesn't really help much in this regard. There is a proper static typing system for Clojure[0] that does provide a lot of the editor integration you speak of, but as I recall it was a little too brittle and orthogonal to Clojure's way of doing things to be as useful as spec. Some of Clojure's core constructs are completely impossible to type statically. As with everything there are tradeoffs and choices to be made. I've been writing Clojure professionally for 5+ years now and there's no other language I have much interest in dealing with full-time (yet). One has to choose one's poison I suppose. [0]: https://github.com/typedclojure/typedclojure