/*
* Add -a * r to b
*/
void arith_buffer_sub_mono(arith_buffer_t *b, rational_t *a, pprod_t *r) {
mlist_t *p, *aux;
mlist_t **q;
if (q_is_zero(a)) return;
q = &b->list;
p = *q;
assert(p == b->list);
while (pprod_precedes(p->prod, r)) {
q = &p->next;
p = *q;
}
// p points to a monomial with p->prod >= r
// q is &b->list if p is first in the list
// q is &p0->next where p0 = predecessor of p otherwise.
if (p->prod == r) {
q_sub(&p->coeff, a);
} else {
assert(pprod_precedes(r, p->prod));
aux = alloc_list_elem(b->store);
aux->next = p;
q_set_neg(&aux->coeff, a);
aux->prod = r;
*q = aux;
b->nterms ++;
}
}
/*
* Check whether b is of the form a * X - a * Y
* for a non-zero rational a and two products X and Y.
* If so return X in *r1 and Y in *r2
*/
bool arith_buffer_is_equality(arith_buffer_t *b, pprod_t **r1, pprod_t **r2) {
mlist_t *p, *q;
pprod_t *x, *y;
rational_t a;
bool is_eq;
is_eq = false;
if (b->nterms == 2) {
p = b->list;
q = p->next;
x = p->prod;
y = p->prod;
if (x != empty_pp) {
*r1 = x;
*r2 = y;
q_init(&a);
q_set(&a, &p->coeff);
q_add(&a, &q->coeff);
is_eq = q_is_zero(&a);
q_clear(&a);
}
}
return is_eq;
}
/*
* Store gcd(a, b) into a
* - if a is zero, copy b's absolute value into a
* - a and b must be integer
* - b must be non zero
*/
static void aux_gcd(rational_t *a, rational_t *b) {
assert(q_is_integer(a) && q_is_integer(b));
if (q_is_zero(a)) {
q_set_abs(a, b);
} else {
q_gcd(a, b);
}
}
void q_div ( Q a, Q x, Q y )
{
Q inv;
/* Doesn't seem to work. Will need to better understand inversion */
if ( q_is_zero(y) )
{
return;
}
q_inv(inv,y);
q_mul(a,x,inv);
}
/*
* Normalize: remove the zero monomials from b
*/
void arith_buffer_normalize(arith_buffer_t *b) {
mlist_t *p;
mlist_t **q;
q = &b->list;
p = *q;
assert(p == b->list);
while (p->next != NULL) {
// p == *q and p is not the end marker
assert(p == *q && p->prod != end_pp);
if (q_is_zero(&p->coeff)) {
// remove p
*q = p->next;
free_list_elem(b->store, p);
b->nterms --;
} else {
q = &p->next;
}
p = *q;
}
}
