public string Visit(Subtr node)
 {
     if (node.Size() == 0)
     {
         numMinus++;
         return("");
     }
     return(Visit((dynamic)node[0])
            + Visit((dynamic)node[1])
            + $"    i32.sub\n");
 }
 public void Visit(Subtr node)
 {
     Visit((dynamic)node[0]);
     Visit((dynamic)node[1]);
 }