[ENH] UpArrow as operator

Ivan Tomek ivan.tomek at acadiau.ca
Thu Mar 18 13:37:44 UTC 1999


Is there an important reason why there is no 'special variable' 
(pseudovariable) to refer to the sender of the message (like self, super, 
thisContext)? As things are, callbacks require awkward solutions 
which don't seem to be necessary as the information already is 
available.

Date forwarded: 	18 Mar 1999 09:42:21 -0000
To:             	squeak at cs.uiuc.edu
Subject:        	Re: [ENH] UpArrow as operator 
Date sent:      	Thu, 18 Mar 1999 10:37:02 +0100
From:           	Marcel Weiher <marcel at system.de>
Send reply to:  	marcel at system.de
Forwarded by:   	squeak at cs.uiuc.edu

> Hmm, is there anything you hadn't already done in '72 ? :-)
> 
> It would be very interesting to hear what some of the implications  
> were, and why the change was made to simple returns (presumably to  
> simplify the implementation and usage patterns for the common case).
> 
> My explorations into iteration have led me to the conclusion that  
> this meaning of the 'return' construct would greatly simplify that  
> area by making it possible to encapsulate even very complicated  
> traversals, and it turns out that the iteration constructs of the  
> Sather language do something very similar (though not as generally).   
> Another application is backtracking (which, I think, corresponds to  
> a 'traversal' over an implicit structure representing the  
> computation).
> 
> Combining the ideas of (a) getting multiple results from a single  
> message send (a dynamic collection) and (b) sending messages to  
> multiple objects makes for a *very* powerful programming model that  
> is still conceptually as simple as the original ST message send.
> 
> Marcel
> 
> > From: Alan Kay <Alan.C.Kay at disney.com>
> >
> > Interesting transitions ...
> >
> > In an early Smalltalk conception, what is now the up arrow was a symbol 
> > that stood for the sender object, i.e. it was a special symbol with a 
> > special meaning (like self), so you were "sending-back" the result. 
> >
> > (And, in the earliest "one-pager" of Smalltalk, sending and receiving 
> > were
> > actually symmetric: one "sentback" the result(s) to the original sender 
> > which could "takeback" and bind the (possibly multiple) result(s).) 
> 



Ivan Tomek,

Jodrey School of Computer Science
Acadia University
Nova Scotia, Canada

fax: (902) 585-1067
voice: (902) 585-1467


Life would be so much easier if we could just look at the source code.
Go Smalltalk.





More information about the Squeak-dev mailing list