On Wed, Jan 14, 2009 at 4:43 PM, Reinier Zwitserloot <[email protected]>wrote:
> You could graft long returns on
> FCM or CICE later, but once you've already used 'return' for the
> notion of a local return, then a future long return addition can never
> be transparent - you'd have to have a different syntax for returning
> out of the containing block, which all by itself is a pretty big
> negative mark - that would mean that any attempt to add language
> features by way of just writing a utility method are permanently
> crippled by the fact that the 'return' syntax is not transparent, and
> thus the need to know that something is a library call instead of a
> language feature will always be a leaky abstraction.
>
There are probably other ways to implement this. If you could, say, call
methods without parenthesis like in Scala, and had a nice way of exposing
those methods to the closure you could implement any behavior you want, and
call it what you want, instead of being restricted to return and friends.
Implementing long return in this way is just the matter of throwing an
exception and catch it at the right place.
Something like
abstract class ControlClosure<T>
{
protected T return(T retval) throws LongReturn<T>{
throw new LongReturn<T>(retval);
}
}
abstract class MyForeach<T>
{
public <RV> void foreach(#ControlClosure<RV>(void(T)LongReturn<RV>)
closure);
}
BR,
John
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