block-lambda revival

Brendan Eich brendan at
Thu Jun 23 23:37:18 PDT 2011

On Jun 23, 2011, at 11:33 PM, Axel Rauschmayer wrote:

> I take it their complaint was *not* about performance? I would think that block lambdas would not use a function + bind to achieve lexical this, but some kind of variable renaming/alpha conversion. Thus, performance should not be an anti-lambda argument. On the other hand, |this| not being stored in an environment, alpha conversion might not work (move |this| from the Execution Context State to an the environment???).

No, block-lambda this access would be like any other upvar, well-optimized.

Performance was not the objection.

>> This is a difference in risk evaluation or tolerance, perhaps. We should try to get to the bottom of it.
> Maybe there should be a list of “functions in all their current use-cases”. I keep thinking that dynamic |this| only matters for methods, but you provided a counter-example.

You are right to push on the question of use-cases. Will try to get a survey done -- Mozilla has several practical analyze-the-web irons in the fire.


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