Finds and returns an edge in a graph given two items.
capi
find-graph-edge graph from to => edge
graph
A graph-pane.
from
An item in graph .
to
edge
A graph edge, or nil .
nil
The generic function find-graph-edge finds the edge that goes from the node corresponding to from to the node corresponding to to .
find-graph-edge
If there is no such edge, find-graph-edge returns nil .
find-graph-node graph-pane