[Seaside] Some questions about Seaside architecture

[Avi Bryant]

On Dec 13, 2005, at 4:31 AM, Oleg Mürk wrote:
>
> Conclusions:
> * Continuations are syntactical sugar for the end-programmer (using  
> framework).
>   The framework could be easily implemented with only event- 
> handlers, using CPS,
>   if needed.
>
> * Back-button support could be implemented also in any event-based  
> without using
>   continuations. This point is important, IMO, becase proper back- 
> button support
>   is often attributed as being possible only with continuation- 
> based frameworks.

Oleg,

Yes, this point is important.  Obviously it's possible to support the  
back button without continuations - the vast majority of web  
applications don't use continuations and yet still support the back  
button.  But the important point is that it's impossible to both get  
blocking control flow *and* support the back button without  
continuations.  That is, without continuations you have to choose  
between:

a) Not have blocking control flow but have back button support (using  
event  handlers, for example)
b) Have blocking control flow, but no back button support (using  
threads)

Above you're indicating that you're comfortable with choice a),  
elsewhere you seem to indicate that you'd also be comfortable with  
choice b).  These may be restrictions that you can personally live  
with, but it's simply incorrect to say that what continuations  
provide over either one is sugar: having both blocking control flow  
and back button support is strictly, formally, more expressive than  
missing one or the other.  And that's an expressivity that most of us  
on this list have found to be extremely useful in practice, and would  
be rather loathe to give up...

Avi