 
 HELP: <bfs>
 { $values
-  { "neighbours" "an assoc" }
-  { "astar" "a astar tuple" }
+  { "neighbours" assoc }
+  { "astar" astar }
 }
 { $description "Build an astar object from the " { $snippet "neighbours" } " assoc. "
   "When used with " { $link find-path } ", this astar tuple will use the breadth-first search (BFS) "

{ $values
  { "start" "a node" }
  { "target" "a node" }
  { "astar" "a astar tuple" }
  { "path/f" "an optimal path from " { $snippet "start" } " to " { $snippet "target" }
    ", or f if no such path exists" }
}

  { "neighbours" "a quotation with stack effect ( node -- seq )" }
  { "cost" "a quotation with stack effect ( from to -- cost )" }
  { "heuristic" "a quotation with stack effect ( pos target -- cost )" }
  { "astar" astar }
}
{ $description "Build an astar object from the given quotations. The "
  { $snippet "neighbours" } " one builds the list of neighbours. The "
