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ecf6d3c6ce
Currently, attributes for `no-panic` are gated behind both the `test` config and `assert_no_panic`, because `no-panic` is a dev dependency (so only available with test configuration). However, we only emit `assert_no_panic` when the test config is also set anyway, so there isn't any need to gate on both. Replace gates on `all(test, assert_no_panic)` with only `assert_no_panic`. This is simpler, and also has the benefit that attempting to check for panics without `--test` errors.
78 lines
2.3 KiB
Rust
78 lines
2.3 KiB
Rust
// origin: FreeBSD /usr/src/lib/msun/src/s_cos.c */
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//
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// ====================================================
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// Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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//
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// Developed at SunPro, a Sun Microsystems, Inc. business.
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// Permission to use, copy, modify, and distribute this
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// software is freely granted, provided that this notice
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// is preserved.
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// ====================================================
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use super::{k_cos, k_sin, rem_pio2};
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// cos(x)
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// Return cosine function of x.
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//
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// kernel function:
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// k_sin ... sine function on [-pi/4,pi/4]
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// k_cos ... cosine function on [-pi/4,pi/4]
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// rem_pio2 ... argument reduction routine
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//
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// Method.
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// Let S,C and T denote the sin, cos and tan respectively on
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// [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
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// in [-pi/4 , +pi/4], and let n = k mod 4.
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// We have
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//
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// n sin(x) cos(x) tan(x)
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// ----------------------------------------------------------
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// 0 S C T
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// 1 C -S -1/T
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// 2 -S -C T
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// 3 -C S -1/T
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// ----------------------------------------------------------
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//
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// Special cases:
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// Let trig be any of sin, cos, or tan.
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// trig(+-INF) is NaN, with signals;
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// trig(NaN) is that NaN;
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//
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// Accuracy:
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// TRIG(x) returns trig(x) nearly rounded
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//
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/// The cosine of `x` (f64).
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///
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/// `x` is specified in radians.
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#[cfg_attr(assert_no_panic, no_panic::no_panic)]
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pub fn cos(x: f64) -> f64 {
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let ix = (f64::to_bits(x) >> 32) as u32 & 0x7fffffff;
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/* |x| ~< pi/4 */
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if ix <= 0x3fe921fb {
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if ix < 0x3e46a09e {
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/* if x < 2**-27 * sqrt(2) */
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/* raise inexact if x != 0 */
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if x as i32 == 0 {
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return 1.0;
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}
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}
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return k_cos(x, 0.0);
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}
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/* cos(Inf or NaN) is NaN */
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if ix >= 0x7ff00000 {
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return x - x;
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}
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/* argument reduction needed */
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let (n, y0, y1) = rem_pio2(x);
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match n & 3 {
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0 => k_cos(y0, y1),
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1 => -k_sin(y0, y1, 1),
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2 => -k_cos(y0, y1),
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_ => k_sin(y0, y1, 1),
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}
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}
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