Collector's accumulator

[Jose]

In the days of the earliest builds, I asked for something like this:


polyline.nodes().cumulate((p0,p1)->new Segment(p0,p1))


to get the segments of a polyline, out from the vertices. 


I read the docs of the b83 but is seems that the Collector accumulator 
does not support bifuncions on the form:

               (U,U)-->V

but only mixed type arguments, (V,U)-->V.

Any alternative?