How do you component split a roof with the eave, hip, valley, ridge selectors in CityEngine?

[GregoryStavish]

Does anybody know how to use the eave, hip, valley, and ridge selectors when designing roofs in CityEngine. I have not been able to successfully comp (f) a roof with these. Can somebody provide me an example in CGA that works? My goal is to give a hip roof, for example, a little more personality by customizing its edges.

Help - 

[CherylLau]

The roof edge selectors (eave, hip, valley, ridge) should be used with comp(e) to extract the edges.

This code creates a hip roof and creates green edges along the eave edges.

edge_width = 0.2

Lot -->
     roofHip(30) Roof.
     comp(e) { eave: Edge }
     
Edge -->
     color(0,1,0)
     s('1, edge_width, edge_width)
     center(yz)
     primitiveCube
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