&zip

[Rod Adams]

I'm trying to define zip(), but can't come up with a signature for a 
function that returns a lazy list of lvalues, but the list itself is not 
lazy?

As a second matter, can you declare a type for the elements of a slurpy 
array?

So far I have:
multi sub zip (Array [EMAIL PROTECTED]) returns List {
  gather {
    while any(@lists) {
      for @lists -> @list {
        take shift @list;
      }
    }
  }
}
But I can't tackle the lvalue problem.
btw, I'm defining the semantics of some of several functions by simply 
supplying a reference implementation.