Tree = type(NodeData) variant {
  LEAF(data:: NodeData),
  GROUP(nodes:: [ref(Tree(NodeData))])
}

Guard = type variant {
  a, b
}.

DecisionTree = type Tree(Guard).

buildTable = function(nodes:: [DecisionTree], size:: i32):: [ DecisionTree ] 
{
  tableInit = arr_create(size):: [DecisionTree].
  
  loop fold(nodes->node:: DecisionTree, tableInit->table):: [DecisionTree]
  {
    switch variant(node):: [DecisionTree]
      case (LEAF)  { table + { LEAF(node["data"]) } }
      case (GROUP) { table + GROUP(buildTable(nodes["nodes"])) }
  }
}