Graph traversal

[tampler]

Hello

I wanna traverse an AST-based graph and call some method for each node. I made some impl, but can't call the node method, since I"m getting `NodeT` in return.

```scala

final case class NodeA(id: Int, op: Function1[Int, Int]) extends AST

final case class NodeB(id: Int, op: Function1[Int, Int]) extends AST

sealed trait AST extends Product with Serializable val g = Graph.from(nodes, edges) val root = g.get(n0) // Traverse graph def procNode(node: g.NodeT): Unit = println(node) root.innerEdgeTraverser.map(_.foreach(procNode)) ``` However, If I try to do something like: ```scala def procNode(node: g.NodeT):Unit = node.id + 1 ``` I'm getting compile error, since node is of type `g.NodeT`. How do I implement `procNode` correctly ? Thank you!

[Peter Empen]

Your graph knows about the node type AST but not its subclasses. So you need either

sealed trait AST {
  def id: Int
}

or match against node.value. That's all.

Btw., case classes do extend Serializable and also Product.

[Peter Empen]

You may want to go with

root.innerNodeTraverser foreach procNode

[Daniel Sobral]

If you don't want NodeT, why not do an *outer* traversal instead? Or, for that matter, just calling ".outer" on the node before passing it to procNode?

-- 

Daniel C. Sobral

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[tampler]

Thanks for a prompt reply guys. Worked like a charm for me.

Here's my final code. The full source is here : https://github.com/Neurodyne/zio-cookbook/blob/master/src/main/scala/graph/Graph.scala

sealed trait AST            

final case class NodeA(id: Int, op: Function1[Int, Int]) extends AST {

def run(): Unit = println(">>>>> Run A")

}

final case class NodeB(id: Int, op: Function1[Int, Int]) extends AST {

def run(): Unit = println(">>>>> Run B")

}

// Traverse graph nodes def procNode(node: g.NodeT): Unit = node.value match {   case n: NodeA => n.run()   case n: NodeB => n.run()   case _        => } root.innerNodeTraverser.foreach(procNode)

 

On Wednesday, April 15, 2020 at 6:58:18 PM UTC+3, Daniel Sobral wrote:

If you don't want NodeT, why not do an *outer* traversal instead? Or, for that matter, just calling ".outer" on the node before passing it to procNode?

-- 

Daniel C. Sobral

On Wed, Apr 15, 2020 at 5:50 AM tampler <socne...@gmail.com> wrote:

Hello

I wanna traverse an AST-based graph and call some method for each node. I made some impl, but can't call the node method, since I"m getting `NodeT` in return.

```scala

final case class NodeA(id: Int, op: Function1[Int, Int]) extends AST

final case class NodeB(id: Int, op: Function1[Int, Int]) extends AST

sealed trait AST extends Product with Serializable val g = Graph.from(nodes, edges) val root = g.get(n0) // Traverse graph def procNode(node: g.NodeT): Unit = println(node) root.innerEdgeTraverser.map(_.foreach(procNode)) ``` However, If I try to do something like: ```scala def procNode(node: g.NodeT):Unit = node.id + 1 ``` I'm getting compile error, since node is of type `g.NodeT`. How do I implement `procNode` correctly ? Thank you!

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