/*
 * listas.c
 * Recursive descencent Parser for Abstract Grammars
 */
 
#include <stdio.h>
#include "tokens.h"

extern int yylex();

static int prox_simb;

int da_simbolo()
{ return yylex(); } 

rec_term(int simb)
{

  if(prox_simb == simb)
  { 
    prox_simb = da_simbolo();
  }  
  else{
    fprintf(stderr, "ERROR: unexpexpected token = %d",prox_simb);
    exit(1);
  }
}


void error()
{ fprintf(stderr, "ERROR: Syntactic, near - %d", prox_simb);
  exit(2);
}


/* ----
   Parser functions declaration
   ----
*/

/* ------------------------------------------- */
/* ----
   TOKENIZER - debug only
   -----
*/

void tokenizer()
{
while(prox_simb)
  {
    printf("%d\n",prox_simb);
    prox_simb=da_simbolo();
  }
  exit(0);
}


/* ------------------------------------------- */
/* ----
   THE PARSER
   -----
*/

main()
{

  prox_simb = da_simbolo();
  tokenizer();
} 


rec_Gabs()
{
  rec_term(OGA);
  rec_BlockList();
  rec_term(CGA);
}


rec_BlockList()
{
  rec_Block();
  rec_BList2();
}


rec_BList2()
{
  switch(prox_simb)
  {
    case CGA: break;
    case SEP: rec_term(SEP);
              rec_Block();
              rec_BList2();
              break;
    default: error();
  }
}


rec_Block()
{
  rec_term(SIMBN);
  rec_term(ODLIST);
  rec_DList();
}


rec_DList()
{
  rec_Deriv();
  rec_DList2();
}


rec_DList2()
{
  switch(prox_simb)
  { case CGA:
    case SEP: break;
    case SEPDLIST: rec_term(SEPDLIST);
                   rec_Deriv();
                   rec_DList2();
                   break;
    default: error();
  }
}


rec_Deriv()
{
  rec_term(ID);
  rec_term(ODER);
  rec_SimbList();
  rec_term(CDER);
}


rec_SimbList()
{
  switch(prox_simb)
  { case CDER: break;
    case SIMBN:
    case SIMBT: rec_Simb();
                rec_SimbList();
                break;
    default: error();
  }
}


rec_Simb()
{
  switch(prox_simb)
  { case SIMBN: rec_term(SIMBN);
                break;
    case SIMBT: rec_term(SIMBT);
                break;
    default: error();
  }
}