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/* origin: FreeBSD /usr/src/lib/msun/src/s_tanf.c */
/*
* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
* Optimized by Bruce D. Evans.
*/
/*
* ====================================================
* 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 core::f64::consts::FRAC_PI_2;
use super::{k_tanf, rem_pio2f};
/* Small multiples of pi/2 rounded to double precision. */
const T1_PIO2: f64 = 1. * FRAC_PI_2; /* 0x3FF921FB, 0x54442D18 */
const T2_PIO2: f64 = 2. * FRAC_PI_2; /* 0x400921FB, 0x54442D18 */
const T3_PIO2: f64 = 3. * FRAC_PI_2; /* 0x4012D97C, 0x7F3321D2 */
const T4_PIO2: f64 = 4. * FRAC_PI_2; /* 0x401921FB, 0x54442D18 */
/// The tangent of `x` (f32).
///
/// `x` is specified in radians.
#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
pub fn tanf(x: f32) -> f32 {
let x64 = x as f64;
let x1p120 = f32::from_bits(0x7b800000); // 0x1p120f === 2 ^ 120
let mut ix = x.to_bits();
let sign = (ix >> 31) != 0;
ix &= 0x7fffffff;
if ix <= 0x3f490fda {
/* |x| ~<= pi/4 */
if ix < 0x39800000 {
/* |x| < 2**-12 */
/* raise inexact if x!=0 and underflow if subnormal */
force_eval!(if ix < 0x00800000 {
x / x1p120
} else {
x + x1p120
});
return x;
}
return k_tanf(x64, false);
}
if ix <= 0x407b53d1 {
/* |x| ~<= 5*pi/4 */
if ix <= 0x4016cbe3 {
/* |x| ~<= 3pi/4 */
return k_tanf(if sign { x64 + T1_PIO2 } else { x64 - T1_PIO2 }, true);
} else {
return k_tanf(if sign { x64 + T2_PIO2 } else { x64 - T2_PIO2 }, false);
}
}
if ix <= 0x40e231d5 {
/* |x| ~<= 9*pi/4 */
if ix <= 0x40afeddf {
/* |x| ~<= 7*pi/4 */
return k_tanf(if sign { x64 + T3_PIO2 } else { x64 - T3_PIO2 }, true);
} else {
return k_tanf(if sign { x64 + T4_PIO2 } else { x64 - T4_PIO2 }, false);
}
}
/* tan(Inf or NaN) is NaN */
if ix >= 0x7f800000 {
return x - x;
}
/* argument reduction */
let (n, y) = rem_pio2f(x);
k_tanf(y, n & 1 != 0)
}