int sg_big_float_trunc(sg_big_float_t* dst, const sg_big_float_t* src)
{
if (!dst || !src)
return -1;
mpf_trunc(dst->mpf, src->mpf);
return 0;
}
// Computes q = exp(2 pi i tau).
static void compute_q(mpc_t q, mpc_t tau) {
mpc_t z0;
mpf_t f0, f1;
mpf_ptr fp0;
pbc_mpui pwr;
mpc_init(z0);
mpf_init(f0);
mpf_init(f1);
//compute z0 = 2 pi i tau
mpc_set(z0, tau);
//first remove integral part of Re(tau)
//since exp(2 pi i) = 1
//it seems |Re(tau)| < 1 anyway?
fp0 = mpc_re(z0);
mpf_trunc(f1, fp0);
mpf_sub(fp0, fp0, f1);
mpc_mul_mpf(z0, z0, pi);
mpc_mul_ui(z0, z0, 2);
mpc_muli(z0, z0);
//compute q = exp(z0);
//first write z0 = A + a + b i
//where A is a (negative) integer
//and a, b are in [-1, 1]
//compute e^A separately
fp0 = mpc_re(z0);
pwr = mpf_get_ui(fp0);
mpf_pow_ui(f0, recipeulere, pwr);
mpf_add_ui(fp0, fp0, pwr);
mpf_exp(f1, mpc_re(z0));
mpf_mul(f0, f1, f0);
mpc_cis(q, mpc_im(z0));
/*
old_mpc_exp(q, z0);
*/
mpc_mul_mpf(q, q, f0);
mpc_clear(z0);
mpf_clear(f0);
mpf_clear(f1);
}
