libm/math/
tanf.rs

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1/* origin: FreeBSD /usr/src/lib/msun/src/s_tanf.c */
2/*
3 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
4 * Optimized by Bruce D. Evans.
5 */
6/*
7 * ====================================================
8 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
9 *
10 * Developed at SunPro, a Sun Microsystems, Inc. business.
11 * Permission to use, copy, modify, and distribute this
12 * software is freely granted, provided that this notice
13 * is preserved.
14 * ====================================================
15 */
16
17use core::f64::consts::FRAC_PI_2;
18
19use super::{k_tanf, rem_pio2f};
20
21/* Small multiples of pi/2 rounded to double precision. */
22const T1_PIO2: f64 = 1. * FRAC_PI_2; /* 0x3FF921FB, 0x54442D18 */
23const T2_PIO2: f64 = 2. * FRAC_PI_2; /* 0x400921FB, 0x54442D18 */
24const T3_PIO2: f64 = 3. * FRAC_PI_2; /* 0x4012D97C, 0x7F3321D2 */
25const T4_PIO2: f64 = 4. * FRAC_PI_2; /* 0x401921FB, 0x54442D18 */
26
27/// The tangent of `x` (f32).
28///
29/// `x` is specified in radians.
30#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
31pub fn tanf(x: f32) -> f32 {
32    let x64 = x as f64;
33
34    let x1p120 = f32::from_bits(0x7b800000); // 0x1p120f === 2 ^ 120
35
36    let mut ix = x.to_bits();
37    let sign = (ix >> 31) != 0;
38    ix &= 0x7fffffff;
39
40    if ix <= 0x3f490fda {
41        /* |x| ~<= pi/4 */
42        if ix < 0x39800000 {
43            /* |x| < 2**-12 */
44            /* raise inexact if x!=0 and underflow if subnormal */
45            force_eval!(if ix < 0x00800000 { x / x1p120 } else { x + x1p120 });
46            return x;
47        }
48        return k_tanf(x64, false);
49    }
50    if ix <= 0x407b53d1 {
51        /* |x| ~<= 5*pi/4 */
52        if ix <= 0x4016cbe3 {
53            /* |x| ~<= 3pi/4 */
54            return k_tanf(if sign { x64 + T1_PIO2 } else { x64 - T1_PIO2 }, true);
55        } else {
56            return k_tanf(if sign { x64 + T2_PIO2 } else { x64 - T2_PIO2 }, false);
57        }
58    }
59    if ix <= 0x40e231d5 {
60        /* |x| ~<= 9*pi/4 */
61        if ix <= 0x40afeddf {
62            /* |x| ~<= 7*pi/4 */
63            return k_tanf(if sign { x64 + T3_PIO2 } else { x64 - T3_PIO2 }, true);
64        } else {
65            return k_tanf(if sign { x64 + T4_PIO2 } else { x64 - T4_PIO2 }, false);
66        }
67    }
68
69    /* tan(Inf or NaN) is NaN */
70    if ix >= 0x7f800000 {
71        return x - x;
72    }
73
74    /* argument reduction */
75    let (n, y) = rem_pio2f(x);
76    k_tanf(y, n & 1 != 0)
77}
libm/math/tanf.rs

libm/math/
tanf.rs
