On Dec 5, 2008, at 12:49 PM, Allen Wirfs-Brock wrote:
From: Brendan Eich [mailto:[EMAIL PROTECTED]
The return hazard exists in Smalltalk too. What's different here that
makes you choose differently? Of course, there are more choices than
Tennent-to-the-max lambdas or-else classes-as-sugar.
The difference is in the foundation language we are starting with.
Because of the central role of c-style syntactic control constructs
in JavaScript it is unlikely that lambda-based control abstractions
will ever be as important in JavaScript as they are in Smalltalk.
Agreed so far. The long-term plan here would be macros. Post-Harmony
at this point.
[snip] If it is necessary to make a choice I'm inclined to
prioritize enhancing object literals to make them be a better
object/class abstraction mechanisms over enhancing lambdas to make
them a better control abstraction mechanism.
I question the need to make a choice (yet).
I'm actually concerned about usability of lambdas as anything similar
to functions. Say they're added, and they prove popular for control
abstractions and other purposes, including "better functions". Then
not only will completion-value leaks bite people -- misplaced return
probably will too, if "better functions" involves porting existing
code from function to lambda.
This is all speculation, but here's my non-speculative claim: lambda
syntax should not look so much like function syntax if return within
the body behaves completely differently. We would want syntax very
different from function (i.e., not lambda (args) {body} -- sorry,
Peter Michaux). Or else we should revisit the wisdom of applying TCP
to lambdas.
[Smalltalk observations snipped -- thanks for those, they make sense
but I want to keep pushing on what doesn't work in the current
strawman: wiki space.]
Don't get me wrong, I like the semantics of break/continue/return
that have been proposed for JavaScript lambdas but given our legacy
I can see the return hazard being a real problem.
I agree if lambda looks like function or is sold as a "better
function". If it looks more like a block, or something else, that
might mitigate the return hazard. Michael Day wondered if we confined
the body to an expression language -- that would eliminate the return
hazard.
And if it is a choice between enhanced object literals and control
abstracting lambdas I'd probably go with the object literals.
No false dilemmas yet, please!
/be
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