Availability:

`:- use_module(library(ugraphs)).`

(can be autoloaded)-
**vertices**`(+S_Graph, -Vertices)`is**det** - Strips off the neighbours lists of an S-representation to
produce a list of the vertices of the graph. (It is a
characteristic of S-representations that
**every**vertex appears, even if it has no neighbours.).`Vertices`is in the standard order of terms. -
**vertices**`(+S_Graph, -Vertices)`is**det** - Strips off the neighbours lists of an S-representation to
produce a list of the vertices of the graph. (It is a
characteristic of S-representations that
**every**vertex appears, even if it has no neighbours.).`Vertices`is in the standard order of terms.