Hello everyone,

I’m trying to write a function that returns an array with all paths from root to leaves in a binary tree, where each path is an array of symbols.

The tree struct is defined like this:

```
abstract type Node end
struct Branch_Node <: Node
left::Node
right::Node
end
struct Leaf_Node <: Node
end
```

So for this tree

```
tree = Branch_Node(Branch_Node(Branch_Node(Leaf_Node(), Leaf_Node()), Leaf_Node()),Branch_Node(Leaf_Node(), Leaf_Node()))
```

I want the function to return

```
[[:left, :left, :left], [:left, :left, :right], [:left, :right], [:right, :left], [:right, :right]]
```

I can write a function that returns a nested array like this:

```
function get_path_to_leaf(node::Leaf_Node)
return
end
function get_path_to_leaf(node::Branch_Node)
return [[:left, get_path_to_leaf(node.left)], [:right, get_path_to_leaf(node.right)]]
end
```

But I can’t figure out how to unfold the paths into flat arrays. I though something like this:

```
function get_path_to_leaf(node::Leaf_Node)
return []
end
function get_path_to_leaf(node::Branch_Node)
return [[append!([:left], i) for i in get_path_to_leaf(node.left)], [append!([:right], i) for i in get_path_to_leaf(node.right)]]
end
```

would do it, but I get the following error “ERROR: MethodError: Cannot `convert`

an object of type Array{Symbol,1} to an object of type Symbol”

and I’m having no luck debugging it. Sorry for the wall of text, can anyone help?

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