bst tree

bst_tree.erl

-module(bst_tree).
-compile(export_all).

-record(node, {key, val, left = nil, right = nil}).

lookup(Node, Key) when Key =:= Node#node.key ->
  	{ok, Node#node.val};

lookup(Node, Key) when Key < Node#node.key ->
	lookup(Node#node.left, Key);

lookup(Node, Key) when Key > Node#node.key ->
	lookup(Node#node.right, Key);	

lookup(nil, _)  ->
	notfound.

insert(nil, Key, Val) ->
	#node{key = Key, val = Val};

insert(Node, Key, Val) when Key =:= Node#node.key ->
	Node#node{val = Val};

insert(Node, Key, Val) when Key < Node#node.key ->
	Node#node{ left = insert(Node#node.left, Key, Val) };

insert(Node, Key, Val) ->
	Node#node{ right = insert(Node#node.right, Key, Val) }.

output.erl

56> R = bst_tree:insert(nil, "kuba", "oboza").
{node,"kuba","oboza",nil,nil}
57> RR = bst_tree:insert(R, "dan", "palmer"). 
{node,"kuba","oboza",{node,"dan","palmer",nil,nil},nil}
58> RRR = bst_tree:insert(RR, "jono", "langley").
{node,"kuba","oboza",
      {node,"dan","palmer",nil,{node,"jono","langley",nil,nil}},
      nil}
59> RRRR = bst_tree:insert(RRR, "varun", "dev"). 
{node,"kuba","oboza",
      {node,"dan","palmer",nil,{node,"jono","langley",nil,nil}},
      {node,"varun","dev",nil,nil}}
60> RRRRR = bst_tree:insert(RRRR, "emma", "james").
{node,"kuba","oboza",
      {node,"dan","palmer",nil,
            {node,"jono","langley",{node,"emma","james",nil,nil},nil}},
      {node,"varun","dev",nil,nil}}