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/* origin: FreeBSD /usr/src/lib/msun/src/s_sin.c */
/*
* ====================================================
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunPro, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ====================================================
*/
use super::{get_high_word, k_cos, k_sin, rem_pio2};
/// Both the sine and cosine of `x` (f64).
///
/// `x` is specified in radians and the return value is (sin(x), cos(x)).
#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
pub fn sincos(x: f64) -> (f64, f64) {
let s: f64;
let c: f64;
let mut ix: u32;
ix = get_high_word(x);
ix &= 0x7fffffff;
/* |x| ~< pi/4 */
if ix <= 0x3fe921fb {
/* if |x| < 2**-27 * sqrt(2) */
if ix < 0x3e46a09e {
/* raise inexact if x!=0 and underflow if subnormal */
let x1p120 = f64::from_bits(0x4770000000000000); // 0x1p120 == 2^120
if ix < 0x00100000 {
force_eval!(x / x1p120);
} else {
force_eval!(x + x1p120);
}
return (x, 1.0);
}
return (k_sin(x, 0.0, 0), k_cos(x, 0.0));
}
/* sincos(Inf or NaN) is NaN */
if ix >= 0x7ff00000 {
let rv = x - x;
return (rv, rv);
}
/* argument reduction needed */
let (n, y0, y1) = rem_pio2(x);
s = k_sin(y0, y1, 1);
c = k_cos(y0, y1);
match n & 3 {
0 => (s, c),
1 => (c, -s),
2 => (-s, -c),
3 => (-c, s),
#[cfg(debug_assertions)]
_ => unreachable!(),
#[cfg(not(debug_assertions))]
_ => (0.0, 1.0),
}
}
// These tests are based on those from sincosf.rs
#[cfg(test)]
mod tests {
use super::sincos;
const TOLERANCE: f64 = 1e-6;
#[test]
fn with_pi() {
let (s, c) = sincos(core::f64::consts::PI);
assert!(
(s - 0.0).abs() < TOLERANCE,
"|{} - {}| = {} >= {}",
s,
0.0,
(s - 0.0).abs(),
TOLERANCE
);
assert!(
(c + 1.0).abs() < TOLERANCE,
"|{} + {}| = {} >= {}",
c,
1.0,
(s + 1.0).abs(),
TOLERANCE
);
}
#[test]
fn rotational_symmetry() {
use core::f64::consts::PI;
const N: usize = 24;
for n in 0..N {
let theta = 2. * PI * (n as f64) / (N as f64);
let (s, c) = sincos(theta);
let (s_plus, c_plus) = sincos(theta + 2. * PI);
let (s_minus, c_minus) = sincos(theta - 2. * PI);
assert!(
(s - s_plus).abs() < TOLERANCE,
"|{} - {}| = {} >= {}",
s,
s_plus,
(s - s_plus).abs(),
TOLERANCE
);
assert!(
(s - s_minus).abs() < TOLERANCE,
"|{} - {}| = {} >= {}",
s,
s_minus,
(s - s_minus).abs(),
TOLERANCE
);
assert!(
(c - c_plus).abs() < TOLERANCE,
"|{} - {}| = {} >= {}",
c,
c_plus,
(c - c_plus).abs(),
TOLERANCE
);
assert!(
(c - c_minus).abs() < TOLERANCE,
"|{} - {}| = {} >= {}",
c,
c_minus,
(c - c_minus).abs(),
TOLERANCE
);
}
}
}