continuations (was Re: error() or nil, 'error msg')

[Tom N Harris <telliamed@...>]

On Wednesday, September 24, 2014 12:55:15 PM Sean Conner wrote:
>   How is that any different from BASIC's "on error goto ... " statement?
> 
>   Also, you have the ability to jump to labels in an outer function, but it
> involves pcall()/error() ... 

I think the biggest problem with "on error" is that it's an implicit goto. 
Jumps should be explicit, and the labels within lexical scope.

The pcall solution does allow us to jump back to a continuation point, but 
it's all-or-nothing where multiple error handlers could trample on each other 
unless there is careful discipline. Not that there's anything wrong with 
careful discipline of course. Also, error() jumps are dynamically scoped.

As Roberto says, a broader goto would be a form of continuation. On the other 
hand, aren't most use cases for continuations also handled by coroutines? The 
one that comes to my mind is futures. In fact, right now the way I see this 
being implemented is by hoisting the function into an implicit coroutine. Then 
what happens if it's part of an explicit coroutine?

-- 
tom <telliamed@whoopdedo.org>