void RingZZ::elem_text_out(buffer &o,
const ring_elem ap,
bool p_one,
bool p_plus,
bool p_parens) const
{
mpz_ptr a = ap.get_mpz();
#warning "possible overflow in large int situations"
char s[1000];
char *str;
bool is_neg = (mask_mpz_cmp_si(a, 0) == -1);
bool is_one = (mask_mpz_cmp_si(a, 1) == 0 || mask_mpz_cmp_si(a, -1) == 0);
int size = static_cast<int>(mpz_sizeinbase(a, 10)) + 2;
char *allocstr = (size > 1000 ? newarray_atomic(char,size) : s);
if (!is_neg && p_plus) o << '+';
if (is_one)
{
if (is_neg) o << '-';
if (p_one) o << '1';
}
else
{
str = mpz_get_str(allocstr, 10, a);
o << str;
}
if (size > 1000) deletearray(allocstr);
}
void RingZZ::syzygy(const ring_elem a, const ring_elem b,
ring_elem &x, ring_elem &y) const
{
// First check the special cases a = 0, b = 1, -1. Other cases: use gcd.
if (RingZZ::is_zero(a))
{
x = RingZZ::from_int(1);
y = RingZZ::from_int(0);
return;
}
mpz_ptr bb = b.get_mpz();
if (mpz_cmp_ui(bb,1) == 0)
{
x = RingZZ::from_int(1);
y = RingZZ::negate(a);
return;
}
if (mask_mpz_cmp_si(bb,-1) == 0)
{
x = RingZZ::from_int(1);
y = RingZZ::copy(a);
return;
}
ring_elem g = RingZZ::gcd(a,b);
y = RingZZ::divide(a,g);
x = RingZZ::divide(b,g);
RingZZ::remove(g);
if (mpz_sgn(x.get_mpz()) > 0)
RingZZ::internal_negate_to(y);
else
RingZZ::internal_negate_to(x);
}
bool QQ::lift(const Ring *Rg, const ring_elem f, ring_elem &result) const
{
// Rg = ZZ ---> QQ
// f is an element of QQ
if (Rg->is_ZZ())
{
gmp_QQ h = MPQ_VAL(f);
if (mask_mpz_cmp_si(mpq_denref(h),1) == 0)
{
result = globalZZ->RingZZ::from_int(mpq_numref(h));
return true;
}
}
return false;
}
bool RingZZ::is_unit(const ring_elem f) const
{
mpz_ptr a = f.get_mpz();
return (mask_mpz_cmp_si(a, 1)==0 ||
mask_mpz_cmp_si(a, -1)==0);
}
