# Coordinates in a free submodule

I am working with free ℤ-modules that are presented a submodules of ℤ^n, for example:

```
A = Matrix([[1, 1, 1]])
V = A.right_kernel()
```

When creating this ℤ-module Sage computes a basis
(in this case `[(1, 0, -1), (0, 1, -1)])`

.

I can also create elements of `V`

as follows :

```
v = V([2, -1, -1])
```

but then I could not find a way to get the coordinates of `v`

in the basis of `V`

.

Is there a function somewhere in Sage that does this?