/*
for large input values use :
arctan(x) = (PI / 2) - arctan(1 / |x|)
and sign of result = sign of original input
*/
void M_arctan_large_input(M_APM rr, int places, M_APM xx)
{
M_APM tmp1, tmp2;
tmp1 = M_get_stack_var();
tmp2 = M_get_stack_var();
M_check_PI_places(places);
m_apm_divide(tmp1, (places + 6), MM_One, xx); /* 1 / xx */
tmp1->m_apm_sign = 1; /* make positive */
m_apm_arctan(tmp2, (places + 6), tmp1);
m_apm_subtract(tmp1, MM_lc_HALF_PI, tmp2);
m_apm_round(rr, places, tmp1);
rr->m_apm_sign = xx->m_apm_sign; /* fix final sign */
M_restore_stack(2);
}
void m_apm_arctan2(M_APM rr, int places, M_APM yy, M_APM xx)
{
M_APM tmp5, tmp6, tmp7;
int ix, iy;
iy = yy->m_apm_sign;
ix = xx->m_apm_sign;
if (ix == 0) /* x == 0 */
{
if (iy == 0) /* y == 0 */
{
M_apm_log_error_msg(M_APM_RETURN, "\'m_apm_arctan2\', Both Inputs = 0");
M_set_to_zero(rr);
return;
}
M_check_PI_places(places);
m_apm_round(rr, places, MM_lc_HALF_PI);
rr->m_apm_sign = iy;
return;
}
if (iy == 0)
{
if (ix == 1)
{
M_set_to_zero(rr);
}
else
{
M_check_PI_places(places);
m_apm_round(rr, places, MM_lc_PI);
}
return;
}
/*
* the special cases have been handled, now do the real work
*/
tmp5 = M_get_stack_var();
tmp6 = M_get_stack_var();
tmp7 = M_get_stack_var();
m_apm_divide(tmp6, (places + 6), yy, xx);
m_apm_arctan(tmp5, (places + 6), tmp6);
if (ix == 1) /* 'x' is positive */
{
m_apm_round(rr, places, tmp5);
}
else /* 'x' is negative */
{
M_check_PI_places(places);
if (iy == 1) /* 'y' is positive */
{
m_apm_add(tmp7, tmp5, MM_lc_PI);
m_apm_round(rr, places, tmp7);
}
else /* 'y' is negative */
{
m_apm_subtract(tmp7, tmp5, MM_lc_PI);
m_apm_round(rr, places, tmp7);
}
}
M_restore_stack(3);
}
void m_apm_arctan_mt(M_APM rr, int places, M_APM aa)
{
m_apm_enter();
m_apm_arctan(rr,places,aa);
m_apm_leave();
}
