func buildInOutPredicateIterator(obj *otto.Object, qs graph.QuadStore, base graph.Iterator, isReverse bool) graph.Iterator {
dir := quad.Subject
if isReverse {
dir = quad.Object
}
lto := iterator.NewLinksTo(qs, base, dir)
hasa := iterator.NewHasA(qs, lto, quad.Predicate)
return iterator.NewUnique(hasa)
}
// predicatesMorphism iterates to the uniqified set of predicates from
// the given set of nodes in the path.
func predicatesMorphism(isIn bool) morphism {
m := morphism{
Name: "out_predicates",
Reversal: func(ctx *context) (morphism, *context) {
panic("not implemented: need a function from predicates to their associated edges")
},
Apply: func(qs graph.QuadStore, in graph.Iterator, ctx *context) (graph.Iterator, *context) {
dir := quad.Subject
if isIn {
dir = quad.Object
}
lto := iterator.NewLinksTo(qs, in, dir)
hasa := iterator.NewHasA(qs, lto, quad.Predicate)
return iterator.NewUnique(hasa), ctx
},
}
if isIn {
m.Name = "in_predicates"
}
return m
}