Note to self: type variables in #purescript and #haskell cannot be bound to partially applied type synonyms.
If you try to do so, in a sufficiently polymorphic way, you'll get very confusing type errors as the checker attempts to solve things with the variable bound to the "head" of the (parametrically expanded) type alias.
Last night it was (forall r. (forall f. Foldable1 f => f a -> r) -> r) and tonight it was (a -> Term a). Introducing a newtype can help, but beware impredicativity.
A great example of how cool PureScript backend optimizer is - The PureScript code makes multiple map and filter calls and also calls into two functions with complicated logic. The generated output shows that the PS code was aggressively inlined into a tiny bit of JS code -
I think next time I might not start in the middle of a large project. Needs to be more like Joy of Painting and start with a blank "canvas". Probably just grab a problem from the cyber-dojo and plug at it.
Let me know if the music is too loud or the font to unreadable.
A weird thing about being 50 is that there are programming languages that I've used regularly for longer than some of the software developers I work with have been alive. I first wrote BASIC code in the 1980s. The first time I wrote an expression evaluator--a fairly standard programming puzzle or homework--was in 1990. I wrote it in Pascal for an undergraduate homework assignment. I first wrote perl in the early 1990s, when it was still perl 4.036 (5.38.2 now). I first wrote java in 1995-ish, when it was still java 1.0 (1.21 now). I first wrote scala, which I still use for most things today, in 2013-ish, when it was still scala 2.8 (3.4.0 now). At various times I've been "fluent" in 8086 assembly, BASIC, C, Pascal, perl, python, java, scala; and passable in LISP/Scheme, Prolog, old school Mathematica, (early days) Objective C, matlab/octave, and R. I've written a few lines of Fortran and more than a few lines of COBOL that I ran in a production system once. I could probably write a bit of Haskell if pressed but for some reason I really dislike its syntax so I've never been enthusiastic about learning it well. I've experimented with Clean, Flix, Curry, Unison, Factor, and Joy and learned bits and pieces of each of those. I'm trying to decide whether I should try learning Idris, Agda, and/or Lean. I'm pretty sure I'm forgetting a few languages. Bit of 6502 assembly long ago. Bit of Unix/Linux shell scripting languages (old enough to have lived and breathed tcsh before switching to bash; I use fish now mostly).
When I say passable: in graduate school I wrote a Prolog interpreter in java (including parsing source code or REPL input), within which I could run the classic examples like append or (very simple) symbolic differentiation/integration. As an undergraduate I wrote a Mathematica program to solve the word recognition problem for context-free formal languages. But I'd need some study time to be able to write these languages again.
I don't know what the hell prompted me to reminisce about programming languages. I hope it doesn't come off as a humblebrag but rather like old guy spinning yarns. I think I've been through so many because I'm never quite happy with any one of them and because I've had a varied career that started when I was pretty young.
I guess I'm also half hoping to find people on here who have similar interests so I'm going to riddle this post with hashtags:
@abucci I didn't write an interpreter until college, but I also started with BASIC in the 80s.
Currently writing #haskell for work and #purescript (and Haskell) when I'm not on the clock. Previously did everything from PHP or PowerBuilder to C and C++ to Java and Scala or C#.
Really want a practical language based on Graded Modal Dependent Type Theory so putting some of my spare cycles into playing with that. Interested in having safe+easy lexical capture AND GC-free execution regions.
@Profpatsch Oof, pass. I got really stoked around typescript for a little while, but they stopped maintaining the spec, and these days I greatly prefer #Purescript if I have to target a browser and have a choice. (It doesn't have a spec either, but I find it a much nicer language.)
At work, we still just do JS, but that's because it's likely to come out of a julius splice from #Yesod.
Bah, #purescript doesn't call it "strict positivity", but it doesn't let me violate that and derive Functor. Sometimes I think the "efficient DeBruijn" of #bound 's Scope gets paid for in programmer time. :blobfoxlaughsweat:
I've got a specific type that uses a #bound approach but I'd like to write some general folds (using e.g. algebra families) instead of duplicating the "traversal" code.
I might have done the categorical approach (functor categories instead of algebra families) before, but that has limitations and I think I lost the code.
Having to deal with type conflicts at runtime is exhausting to me. Writing non-trivial JS at work is a slog. But, I'd say #purescript is almost as much fun as #ghc#haskell and might be better-specified!
Updated my ugly-ass lambda calculus thing on my website (https://www.iguanasuicide.net/) and now you can click the name of the reduction to perform it.
Typed holes (in #purescript or GHC #haskell or wherever) are just too useful. I don't know how to operate in higher-order / heavily polymorphic code without them anymore. :blobfoxgooglyconfused:
Writing a new language is hard... so much to implement before I'm even willing to use it myself! 😜
Anyone know of an interactive "lambda calculus" expression evaluation site? Or something in that UX neighborhood that I should use for inspiration?
I know I used to answer a lot of #haskell questions just by stepping though evaluation. I thought it would be nice to have that on a website and I have a basic expression parser and visualizer in #purescript running on my website ("production" is a buggy version, tho) but need to design interactive stepping.
Basically, I understand the concepts of functional programming quite well and can also programme #purescript or #haskell relatively confidently. But when it comes to #typelevel programming, I haven't quite got over this threshold yet. I would really like to understand everything better and learn more in this area, because many cool libraries are based on it.
@pitmutt If you haven't tried it, yet, try #Purescript and Halogen for your rich pages or SPAs. (I still prefer Haskell for routing, non-trivial backend, or multi-endpoint APIs; Servant is great.)