[pmontra]

This feature is not so bad:

> In case you really need to vary a variable, the when keyword lets you check a variable each time it mutates.

  const var health = 10!
  when (health = 0) {
    print("You lose")!
  }

If it can really be triggered when the variable changes to any value it makes it a truly reactive paradigm programming language. By the way, could that be hacked to implement loops?

  const var i = 10
  when (i >= 0) {
    do_something()
    i = i  - 1
  }

[pmontra]

Yes, when is the way to do loops in this language. From the hidden examples page

  functi fibonacci (n) => {
     const var sum = 1!
     const var i = 0!
     when (i < n) {
        sum += sum + previous sum!
        i++!
     }
  }

  when (i < 10) {
     fibonacci(i)?
     i++!
  }

[ravi-delia]

And if you don't want your code to loop back by accident you can just use lifetimes! Truly an elegant language

[Doxin]

Oh please tell me you can specify the length of your loops in lines of code executed.

[ravi-delia]

  var var i<10> = 0!!
  var var i = false!
  when (i) {
    print(i)!
    i++!
  }

I think this should print 0,1,2 and then stop, assuming checking the condition is a line of code, and that lifetimes are for lines executed and not just the syntax.

[ilaksh]

Yeah honestly I was really interested in that. Kind of like a logic language?

Maybe Prolog is the perfect language.

[Jiro]

Isn't that basically a computed COME FROM?

[squeaky-clean]

It's basically a syntactic sugar on an Observer pattern but I like it. You would need a way to turn off 'when' observers. And I suppose it does couple the observer to the observable pretty tightly.

[pmontra]

Delete the observed variable?

About coupling, an implementation could send state change events to a message bus and observers could subscribe only the events they care about.

[SamBam]

It's pretty easy to turn off the when observers, simply `delete when`.

Side-effect is that it will delete all the whens, so only use it if you need it!

[krackers]

This feels sort of like key-value observation in obj-c

[epistasis]

I like this feature, but to really make it pop I would like it to be combined with comefrom control flow.

[mhd]

Doesn't Tcl's "trace" feature do this?

[hoosieree]

Looks a little like FRP.