On 4/17/12 10:03 PM, David Piepgrass wrote:
> This requires arbitrary lookahead to disambiguate from tuples.
This bit in particular. Really really don't want to cross the
bridge to
arbitrary lookahead in the grammar.
Pardon me, but I'm not convinced that there is a problem in lambdas
like (x, y) -> (x + y). By analogy, you can realize that ((x * y) + z,
q) is a tuple instead of a simple parenthesized expression when you
reach the comma -- you don't need to look ahead for a comma in
advance. So why not treat (x, y) as a tuple until you reach the "->"
and then reinterpret the contents at that point? This works as long as
the syntax of a lambda argument list is a subset of the tuple syntax,
anyway. If that's not the case, parsing gets messier, though I'm sure
arbitrary lookahead is not be the only possible implementation.
You are correct that, in theory, we could parse, but we wouldn't be able
to build AST nodes until we know definitively whether it's a lambda or not.
Niko
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