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use super::{fabs, get_high_word, get_low_word, sqrt, with_set_low_word};
const PIO2_HI: f64 = 1.57079632679489655800e+00;
const PIO2_LO: f64 = 6.12323399573676603587e-17;
const P_S0: f64 = 1.66666666666666657415e-01;
const P_S1: f64 = -3.25565818622400915405e-01;
const P_S2: f64 = 2.01212532134862925881e-01;
const P_S3: f64 = -4.00555345006794114027e-02;
const P_S4: f64 = 7.91534994289814532176e-04;
const P_S5: f64 = 3.47933107596021167570e-05;
const Q_S1: f64 = -2.40339491173441421878e+00;
const Q_S2: f64 = 2.02094576023350569471e+00;
const Q_S3: f64 = -6.88283971605453293030e-01;
const Q_S4: f64 = 7.70381505559019352791e-02;
#[inline]
fn comp_r(z: f64) -> f64 {
let p = z * (P_S0 + z * (P_S1 + z * (P_S2 + z * (P_S3 + z * (P_S4 + z * P_S5)))));
let q = 1.0 + z * (Q_S1 + z * (Q_S2 + z * (Q_S3 + z * Q_S4)));
p / q
}
#[inline]
#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
pub fn asin(mut x: f64) -> f64 {
let z: f64;
let r: f64;
let s: f64;
let hx: u32;
let ix: u32;
hx = get_high_word(x);
ix = hx & 0x7fffffff;
if ix >= 0x3ff00000 {
let lx: u32;
lx = get_low_word(x);
if ((ix - 0x3ff00000) | lx) == 0 {
return x * PIO2_HI + f64::from_bits(0x3870000000000000);
} else {
return 0.0 / (x - x);
}
}
if ix < 0x3fe00000 {
if ix < 0x3e500000 && ix >= 0x00100000 {
return x;
} else {
return x + x * comp_r(x * x);
}
}
z = (1.0 - fabs(x)) * 0.5;
s = sqrt(z);
r = comp_r(z);
if ix >= 0x3fef3333 {
x = PIO2_HI - (2. * (s + s * r) - PIO2_LO);
} else {
let f: f64;
let c: f64;
f = with_set_low_word(s, 0);
c = (z - f * f) / (s + f);
x = 0.5 * PIO2_HI - (2.0 * s * r - (PIO2_LO - 2.0 * c) - (0.5 * PIO2_HI - 2.0 * f));
}
if hx >> 31 != 0 {
-x
} else {
x
}
}