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I think I read that Wren's creator deliberately avoided "the metaclass hierarchy matches the class hierarchy" (as used in Smalltalk and taken to an extreme in R

by pansa2 1y ago

I think I read that Wren's creator deliberately avoided "the metaclass hierarchy matches the class hierarchy" (as used in Smalltalk and taken to an extreme in Ruby [0]) because the authors of Smalltalk have come to regret that design? I'd be interested to hear more details about the issues with that approach. I've not had any problems with it, and occasionally found it useful. For example, in one situation I needed a hierarchy of static constructors that matched the hierarchy of instance constructors. [0] Ruby also has "the meta-metaclass hierarchy matches the metaclass hierarchy" and "the meta-meta-metaclass hierarchy..." ad infinitum. It's a beautiful design really - it means that in Ruby (unlike Smalltalk), it's always true that "the superclass of the metaclass is the metaclass of the superclass". Edit: Here's the quote I was remembering: > My hunch is that we don't want metaclass inheritance. From talking to a few old Smalltalkers, they generally consider it a mistake there. Also, Java, C++, C#, etc. have semantics more similar to not allowing metaclass inheritance (in other words, static methods aren't inherited), and it seems to work well there. https://groups.google.com/g/wren-lang/c/LkKg51fEUg4/m/0GOK0PCxQr0J https://groups.google.com/g/wren-lang/c/LkKg51fEUg4/m/0GOK0P...

reactordev 1y ago
Static method inheritance is one thing. Member method inheritance (or lack there of) makes it long in the tooth to work with if you want to represent covariant classes that share methods.
- pansa2 1y ago
  Wren does have instance method inheritance. It's implemented differently from most scripting languages, though. The implementation is more like a statically-typed language, for performance reasons: https://wren.io/performance.html#copy-down-inheritance https://wren.io/performance.html#copy-down-inheritance
  - reactordev 1y ago
    So it does have: class A { construct new () {} thing(obj) { … } } class B is A { construct new () {} } B.new().thing(obj) I’ll need to test this as this is what I want from my scripting language. If this works than wren will replace my Lua janky scripting.
    - pansa2 1y ago
      Yes: https://wren.io/try/?code=MYGwhgzhAECC0G8BQ1rAPYDsIBcBOArsDtJgKYDu0AFAJSIC+K0OAFgJaYDm16ARgCt6yVKgDKAT1xkAtgDoADnk45eg2syZMkoSDABC0djHgi0WXIWKlKNYVqRJ9c8hTpy2nHgEZaQA https://wren.io/try/?code=MYGwhgzhAECC0G8BQ1rAPYDsIBcBOArsDt...
      - reactordev 1y ago
        Trying to update a field from a subclass and print the results doesn’t work. class A { name { _name } name=(value){ _name=value } construct new () { _name = "hello" } thing() { System.print(name) } } class B is A { construct new () {} update(name){ super.name = name return this } } var b = B.new() b.update("world").thing() If you change System.print(name) to System.print(_name) it works but it doesn’t when using the getter. You get null when System.print(name) is called. Same if you use this.name
        pansa2 1y ago
        Your `name` getter isn't working properly. Weirdly, Wren's implicit returns only work for functions written on a single line. The getter either needs to be (exactly) `name { _name }` or it needs to explicitly `return _name`. https://wren.io/functions.html#returning-values https://wren.io/functions.html#returning-values
        reactordev 1y ago
        That was it. Nuance in the “no new line after…” parsing. Thanks, it works now. Awesome!

by pansa2 1y ago

reactordev 1y ago

Static method inheritance is one thing. Member method inheritance (or lack there of) makes it long in the tooth to work with if you want to represent covariant classes that share methods.

pansa2 1y ago
Wren does have instance method inheritance. It's implemented differently from most scripting languages, though. The implementation is more like a statically-typed language, for performance reasons: https://wren.io/performance.html#copy-down-inheritance https://wren.io/performance.html#copy-down-inheritance
- reactordev 1y ago
  So it does have: class A { construct new () {} thing(obj) { … } } class B is A { construct new () {} } B.new().thing(obj) I’ll need to test this as this is what I want from my scripting language. If this works than wren will replace my Lua janky scripting.
  - pansa2 1y ago
    Yes: https://wren.io/try/?code=MYGwhgzhAECC0G8BQ1rAPYDsIBcBOArsDtJgKYDu0AFAJSIC+K0OAFgJaYDm16ARgCt6yVKgDKAT1xkAtgDoADnk45eg2syZMkoSDABC0djHgi0WXIWKlKNYVqRJ9c8hTpy2nHgEZaQA https://wren.io/try/?code=MYGwhgzhAECC0G8BQ1rAPYDsIBcBOArsDt...
    - reactordev 1y ago
      Trying to update a field from a subclass and print the results doesn’t work. class A { name { _name } name=(value){ _name=value } construct new () { _name = "hello" } thing() { System.print(name) } } class B is A { construct new () {} update(name){ super.name = name return this } } var b = B.new() b.update("world").thing() If you change System.print(name) to System.print(_name) it works but it doesn’t when using the getter. You get null when System.print(name) is called. Same if you use this.name
      - pansa2 1y ago
        Your `name` getter isn't working properly. Weirdly, Wren's implicit returns only work for functions written on a single line. The getter either needs to be (exactly) `name { _name }` or it needs to explicitly `return _name`. https://wren.io/functions.html#returning-values https://wren.io/functions.html#returning-values
        reactordev 1y ago
        That was it. Nuance in the “no new line after…” parsing. Thanks, it works now. Awesome!