const after initialization / pointers, references and values

[Wyatt via Digitalmars-d]

On Friday, 22 August 2014 at 18:21:06 UTC, Vicente wrote:
>
> @Wyatt:
> Certainly ref parameters help a lot, but I'm trying to get a 
> "Node" by returning (a reference to) it. Does the ref keyword 
> apply to the return type?

I poked it a bit and came out with this.  I _think_ it's working 
as expected:
import std.stdio;
import std.string;

// struct or class
struct Node {
         Node[] block;
         uint num = 0;
};

// static immutable
Node[] default_nodes = [
         {num:3},
         {block:[{num:4},{num:6},{block:[{num:5},{num:7}]}]},
         // ...
];

class NodeProvider{
         // change to const after constructor
         private Node[] nodes;

         private void parse_file(char[] file_name){
                 // initialize nodes from file
                 for(auto i=0; i<3; i++){
                         nodes.length++;
                         nodes[$-1].num=i;
                 }
         }

         this(){
                 nodes = default_nodes;
         }
         this(char[] file_name){
                 parse_file(file_name);
         }

         auto ref opSlice(){return nodes[];};
}

string NodetoString(ref Node n){
         string str = format("%u{ ", n.num);
         foreach(b;n.block)
                 str ~= NodetoString(b);
         str ~= "} ";
         return str;
}

int main(char[][] args){
         NodeProvider np;

         if(args.length==2)
                 np = new NodeProvider(args[1]);
         else
                 np = new NodeProvider();

         foreach(node_ref; np){
                 writeln(NodetoString(node_ref));
         }
         return 0;
}

-Wyatt