void SMat<CoeffRing>::vec_row_op2(sparsevec *&v,
size_t r1, size_t r2,
const elem &a1, const elem &a2,
const elem &b1, const elem &b2) const
// row(r1 in v) := a1 * row(r1 in v) + a2 * row(r2 in v)
// row(r2 in v) := b1 * row(r1 in v) + b2 * row(r2 in v) (RHS refers to previous values)
{
// v[row r1] = a1 * v[r1] + a2 * v[r2]
// v[row r2] = b1 * v[r1] + b2 * v[r2]
elem e1,e2, c1,c2,c3,c4;
ring().set_zero(c1);
ring().set_zero(c2);
ring().set_zero(c3);
ring().set_zero(c4);
bool r1_nonzero = vec_get_entry(v,r1,e1);
bool r2_nonzero = vec_get_entry(v,r2,e2);
if (!r1_nonzero && !r2_nonzero) return;
if (r1_nonzero)
{
ring().mult(c1, a1, e1);
ring().mult(c3, b1, e1);
}
if (r2_nonzero)
{
ring().mult(c2,a2,e2);
ring().mult(c4,b2,e2);
}
ring().add(c1,c1,c2);
ring().add(c3,c3,c4);
vec_set_entry(v,r1,c1);
vec_set_entry(v,r2,c3);
}
bool SMat<CoeffRing>::get_entry(size_t r, size_t c, elem &result) const
// Returns false if (r,c) is out of range or if result is 0. No error
// is returned. result <-- this(r,c), and is set to zero if false is returned.
{
return vec_get_entry(columns_[c], r, result);
}
