Basic Lambdas and Explicit Tail Calls Repackaged

Yuh-Ruey Chen maian330 at gmail.com
Tue Dec 9 03:13:59 PST 2008


I was also under the impression that since lambdas were lighter
functions that would be more efficient in time and/or space.

Brendan Eich wrote:
> We started with lambdas as better functions. They evolved due to a  
> combination of TCP idolatry (sorry, I call it as I see it :-P) and  
> some preference for Scheme-ish modeling of statements as if they were  
> part of an expression language (based on completion value precedent  
> used by eval).
>
> We should back up and reconsider the goals. It seems to me that these  
> two main goals are in conflict:
>
> 1. Better functions, better meaning no |this| parameter and no  
> arguments object, possibly no var. For this item alone, TCP for var,  
> return, etc. seems undesirable. We could ban var, and make return  
> apply to the immediately enclosing lambda, which would thus not be  
> anything comparable to a Smalltalk block.
>
> 2. The ability to desugar existing and future syntax into kernel  
> semantics primarily using lambda coding and lexical bindings. As the  
> for loop desugarings Mark and David-Sarah worked out demonstrate, this  
> item wants var TCP at least, probably the full monty: |this|, return,  
> break, continue all apply to the lexically enclosing function, loop,  
> switch, etc.
>
> About return, break, and continue, I think Michael Day is onto  
> something in arguing that TCP loses when it comes to block-bodied  
> lambdas (if we have such, and we think we should, because the JS  
> expression language is too weak as Jon Zeppieri colorfully asserts).  
> What motivates aggressive TCP application is the second goal.
>
> Is it possible to reconcile these goals? I don't think so. If not,  
> then 1 trumps 2 for a language catering to humans rather than, or  
> primarily over against, code generator programs or a relatively few  
> specifications that want to desugar, no matter the loss of clarity or  
> usability to most hand-coding users of the language. 2 trumps 1 if  
> it's all about Schemers and GWT or Volta or OpenLaszlo or Skynet :-P.
>
> I say 1 trumps 2 for the reason given in the last paragraph: human  
> programmers first, meaning the fat bell curve (sorry, Schemers).
>
> /b


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