FunctionFieldCategoryFunctions2(R1, UP1, UPUP1, F1, R2, UP2, UPUP2, F2)

curve.spad line 412 [edit on github]

Lifts a map from rings to function fields over them.

map : (Mapping(R2, R1), F1) -> F2

map(f, p) lifts f to F1 and applies it to p.