On Thu, Jan 12, 2012 at 5:52 PM, Allen Wirfs-Brock
<al...@wirfs-brock.com> wrote:
>
> On Jan 12, 2012, at 2:23 PM, François REMY wrote:
>
> Am I wrong if I say there not a bigger issue with block lambda than with the
> current object notation on the matter?
>
>
> I think you're correct. An ExpressionStatment can not begin with a {
> so,without changing that rule, there should be no potential for ambiguity
> between Block and BlockLambda. The only issue is distinguishing
> ObjectLiteral and BlockLambda and from that perspective a {( is as good as
> a {| as neither is ambiguous with existing ObjectLiteral syntax,
An additional consideration: for a block lambda's completion value to
be another block lambda, the {( syntax would require parenthesis,
while the {| syntax would not:
let succ =
{(x)
{(s)
{(z)
s(x(s)(z))
}}};
With the grammar François is suggesting, this would be a syntax error
(I think), since the body of a block lambda is a StatementList_opt.
The {| syntax, on the other hand, can accommodate block lambdas as
expression statements, though, given another token of lookahead
(again, I think).
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