:title
Get unique strings

:sig
function unique(items : dval) dval

:returns
This function returns a new list-shaped `dval`.

:content
`unique` keeps the first copy of each string in a list-shaped `dval`.

The result keeps input order. This function does not change `items`.

:example capy render
var items := split("one,two,one", ",")
print(join(unique(items), ","), "\n")

:see-group
collections
