block-lambda revival

Brendan Eich brendan at
Thu Jun 23 15:27:04 PDT 2011

On Jun 23, 2011, at 3:14 PM, Jorge wrote:

>> Anyway, my 2 cents.  Thanks!
> {|| ... } for shorter *function* syntax is my favorite too. +1(e9)

Thanks -- I am continuing to maintain arrow function syntax and block lambda revival as strawmen.

Arrows now require only two-token lookahead, ignoring the #!~ prefixes proposed for non-configurable, non-writable, and non-enumerable property assignments in object initialisers. This is in order to support either an object literal body or a braced non-empty block body where the block's first statement is not a labeled statement.

Block lambda revival has more grammar changes, but so far they check out.

> Also, if any { block } could be a lambda, perhaps we won't need that (nor any new) syntax for block-lambdas.

We would need new syntax still, for formal parameters.

Making blocks be expressions requires unifying the ObjectLiteral and Block productions. I don't know how to do this in without at least two-token lookeahead, and it is not a backward compatible change if done for all places where Statement : Block in the current grammar.

> Also, I'd prefer to know/see clearly when a function is being call()ed, so I'm not very fond of paren-free calls: foo(bar) is clearly an invocation, unlike foo bar,

Your example is too abstracted to be fair. Concretely, the latter will *always* look like foo {|| bar} ... and never foo bar for any bar.

> and readability is more important than saving a few keystrokes.

Readability arguments support the paren-free syntax too. You can't win this by selective arguing.

> The C language is still (and -ISTM- will be for a long time) important, so -IMO- every little bit of JS's C-like syntax is a plus: less to learn: an old, popular, widely used, well-known, and familiar syntax.

C by way of Java, and both are boat anchors. Again, where pray tell is 'function' in C?

> JS -unlike other languages- is important enough that it does not need to follow these (dubious) trendy fashions to become popular. Nor to survive.

Nothing trendy about Smalltalk blocks unless you are a Rubyist.

> Proper punctuation aids comprehension and we're programming, not writing quick SMSs.

This is silly, you're making vague arguments that cut both ways.

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