# Can the star of a ray of a fan be computed in sage?

Let `p`

be a ray of a fan `F`

in a lattice `N`

. Let `Np`

be the quotient lattice `N / N.span(p)`

. The *star* of `p`

is the fan in `Np`

defined by

```
Star(p) = {bar(sigma) | p <= sigma}
```

(This definition is taken from Definition 4.4 on page 55 of this paper. Is there an algorithm to compute `Star(p)`

in `sage`

? If so, what about the embedding morphism `Star(p) --> F`

?