Different semantics should have different-looking syntax

Brendan Eich brendan at mozilla.com
Sat May 21 13:20:30 PDT 2011

On May 21, 2011, at 12:37 PM, Brendan Eich wrote:

> For http://wiki.ecmascript.org/doku.php?id=strawman:block_lambda_revival I have written up the Ruby-inspired {|x| x * x} syntax.
> Alternatives (ignoring keyword issues) that look more like function syntax (Peter's suggestion of lambda (x) { x * x }, e.g.) seem worse in this light: block lambdas do follow the correspondence principle, which is novel to JS with its C statements for control effects heritage.
> In this light, the use of | | to bracket formal parameters seems better than anything using (...) {...}. This is not an overriding concern, but it seems worth mentioning. We want block-lambdas or any such TCP-pure new thing to have syntax that says "look! something new here".
> And, since the strawman builds on block syntax,

Urgh, I meant to write "supports building control abstractions that mimic keyword-head governing block syntax", or something like that. Came off as circular arguing the way I wrote it.

> we want the new form to have syntax that "looks like a block", in which you'd expect TCP purity for break, continue, return, |this|, and arguments.

Point is we want light weight, control abstractions, TCP, lambdas. In the proposal this leads to (a) block lambdas; (b) paren-free calls provided actuals are block lambdas.


> Thus, block lambdas that start with { and have lightweight parameter delimiters.
> /be
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