define macro graph
 { graph ( ?edges:* ) }
    => { begin
           let g = make(<graph>);
           ?edges;
           add-edges(g, list(?connections));
           g;
         end }

    edges:
    { } => { }
    { ?connections ; ... } =>
      { add-edges(g, list(?connections)) }

    connections:
    { ?node:name } => { ?"node" }
    { ?node:name -> ... } { ?"node", ... }
end;