%{
// 
// Graph Generator

/* This parser recognizes the following graph grammar

adjacencyList => nodeAdjacencyList+
nodeAdjacencyList => NODE_NAME -> NODE_NAME "EDGE_LABEL"? 
                          (, NODE_NAME "EDGE_LABEL"?)* ;

*/

#include <stdio.h>
#include <iostream>
#include <string>
#include <stdlib.h>

using namespace std;

// for keeping track of line numbers in the program we are parsing
  int line_num = 1;

// function prototypes, we need the yylex return prototype so C++ won't complain
int yylex();
void yyerror(char * s);

string fromVtx;

%}


%union {
  int num;
  char *name;
  char *lab;
}

%error-verbose

%token <name> NAME
%token <lab> LABEL
%token COMMA SEMI
%token ARROW

%%

adjacencyList : adjacencyList edgeHead SEMI
              | edgeHead SEMI
;

edgeHead : NAME { fromVtx = $1; } ARROW edgeList 

edgeList : edgeList COMMA edge
         | edge
;

edge : NAME {
  cout << fromVtx << " -> " << $1 << ";" << endl;
}
     | NAME LABEL {
  cout << fromVtx << " -> " << $1;
  cout << " [ label = \"" << $2 << "\" ];" << endl;
}
;

 
%%
main()
{
//      yydebug = 1;
  cout << "digraph {" << endl;
  yyparse();
  cout << "}" << endl;
}

void yyerror(char * s)
{
  fprintf(stderr, "line %d: %s\n", line_num, s);
}