/*
 * poly.c
 *
 * This file contains functions for handling polynomials as linked lists
 * of monomials
 */
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "mono.h"
#include "poly.h"

/* make an empty polynomial */

void create_poly (poly *L) {
	*L = NULL;
}

/* get rid of a polynomial, freeing storage */

void destroy_poly (poly *L) {
	polynode	*p;

	p = *L;
	if (!p) return;
	p = p->next;
	free (*L);
	*L = NULL;
	destroy_poly (&p);
}

/* insert a monomial term t at the end of a polynomial L */

void insert_poly (poly *L, mono t) {

	/* recursive voodoo, don't ask */

	if (!*L) {
		*L = (polynode *) malloc (sizeof (polynode));
		(*L)->t = t;
		(*L)->next = NULL;
	} else
		insert_poly (&(*L)->next, t);
}

/* read a polynomial */

poly get_poly (void) {
	poly	L;
	mono 	t;

	create_poly (&L);
	while (!read_mono (&t)) insert_poly (&L, t);
	return L;
}

/* print a polynomial on standard output */

void print_poly (poly L) {
	polynode	*p;

	/* if the first thing is negative, print a minus sign
	 * because later we'll take the absolute value
	 */
	if (L) if (L->t.coeff < 0.0) printf ("- ");

	/* for each monomial... */

	for (p=L; p; p=p->next) {

		/* if the coefficient is 1 or -1, don't print it */

		if (fabs (p->t.coeff) != 1.0 || p->t.power == 0.0) 
			printf ("%.f", fabs (p->t.coeff));

		/* if the power is 0, don't print x */

		if (p->t.power != 0.0 && p->t.coeff != 0.0) {
			printf ("x");
			if (p->t.power != 1.0)
				printf ("^%.f", p->t.power);
		}

		/* if there is something left in the list, print 
		 * the appropriate connector (+ or -)
		 */
		if (p->next) {
			if (p->next->t.coeff < 0.0) 
				printf (" - ");
			else
				printf (" + ");
		}
	}
}