sym_transform_lrec.c

/* ************************************************************************** */
/*                                                                            */
/*                                                        :::      ::::::::   */
/*   sym_transform_lrec.c                               :+:      :+:    :+:   */
/*                                                    +:+ +:+         +:+     */
/*   By: mgautier <mgautier@student.42.fr>          +#+  +:+       +#+        */
/*                                                +#+#+#+#+#+   +#+           */
/*   Created: 2017/11/30 16:04:47 by mgautier          #+#    #+#             */
/*   Updated: 2017/12/04 15:17:24 by mgautier         ###   ########.fr       */
/*                                                                            */
/* ************************************************************************** */

#include "sym_defs.h"
#include "prods_interface.h"
#include "libft.h"
#include <stdlib.h>
#include <stdarg.h>

static t_lst	*take_left_recursive_prods(t_symbol *left_recursive_sym)
{
	return (f_split_lst_va(
				&left_recursive_sym->prods,
				TRUE,
				gen_prod_is_left_recursive,
				left_recursive_sym));
}

static t_bool	remove_left_recur(void *prod, va_list args)
{
	remove_symbols_head(prod, 1);
	return (append_to_prod(prod, va_arg(args, t_symbol const*)));
}

/*
** TODO: Find a way to distinguish between the case where the sym is not left
** recursive and the one where malloc fails.
*/

t_symbol		*eliminate_left_recursion(t_symbol *left_recursive_sym)
{
	t_lst		*left_rec_prods;
	t_symbol	*new_sym;
	t_prod		*empty_prod;

	left_rec_prods = take_left_recursive_prods(left_recursive_sym);
	if (left_rec_prods != NULL)
	{
		new_sym = derivate_new_sym(left_recursive_sym, "LREC");
		if (new_sym != NULL)
		{
			f_lstiterr_va(
					left_recursive_sym->prods, gen_append_to_prod, new_sym);
			new_sym->prods = left_rec_prods;
			f_lstiterr_va(new_sym->prods, remove_left_recur, new_sym);
			empty_prod = create_prod();
			if (empty_prod != NULL)
				add_prod(new_sym, empty_prod);
			else
				destroy_symbol(&new_sym);
		}
	}
	else
		new_sym = NULL;
	return (new_sym);
}