brian.goetz at oracle.com
Sun Feb 26 15:29:30 PST 2012
> Have you considered (I'm sure you have...) a form of requesting the
> reference to have equals semantics? Some form of method call or
> wrapper that the user muist specifically use to get the equals or ==
Yes, there are a number of possible use-site opt-ins to conversion
options we might want to support. One of these is giving a name to a
lambda, which may be useful in a number of contexts.
The syntactic front-runner for this is to put a label inside the
(aLabel: x, y) -> x + y
but this is not yet decided.
Names are a useful part of a number of possible features, including:
more stable serialization, better toString implementations, supporting
nonlocal return, and others.
Another use-site opt-in would be explicit serialization support. While
we plan to do at least as well as inner classes -- a lambda is
serializable if its target type is -- we'd like to do better, and
provide a way of opting in. This largely turns out to be a syntactic
problem -- what is the syntactic form of the opt-in. (Lots of
suggestions have been made, and so far they all suck. I will open this
to suggestions at a future time, but until then, please hold your fire.)
The primary syntactic challenge is that because the conversion is
invisible, there is no obvious place to hang conversion-specific
metadata. We don't want to abuse either the static type system,
annotations, or "fake functions" for this purpose. With a small number
of conversion options we can do something ad-hoc (like the naming
example above) but as the number of conversion options increases, this
starts to hit the wall.
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