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libm/math/
exp10.rs

1use super::{exp2, modf, pow};
2
3const LN10: f64 = 3.32192809488736234787031942948939;
4const P10: &[f64] = &[
5    1e-15, 1e-14, 1e-13, 1e-12, 1e-11, 1e-10, 1e-9, 1e-8, 1e-7, 1e-6, 1e-5, 1e-4, 1e-3, 1e-2, 1e-1,
6    1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6, 1e7, 1e8, 1e9, 1e10, 1e11, 1e12, 1e13, 1e14, 1e15,
7];
8
9/// Calculates 10 raised to the power of `x` (f64).
10#[cfg_attr(assert_no_panic, no_panic::no_panic)]
11pub fn exp10(x: f64) -> f64 {
12    select_implementation! {
13        name: x87_exp10,
14        use_arch_required: x86_no_sse,
15        args: x,
16    }
17
18    let (mut y, n) = modf(x);
19    let u: u64 = n.to_bits();
20    /* fabs(n) < 16 without raising invalid on nan */
21    if ((u >> 52) & 0x7ff) < 0x3ff + 4 {
22        if y == 0.0 {
23            return *P10.get(((n as isize) + 15) as usize).unwrap()i!(P10, ((n as isize) + 15) as usize);
24        }
25        y = exp2(LN10 * y);
26        return y * *P10.get(((n as isize) + 15) as usize).unwrap()i!(P10, ((n as isize) + 15) as usize);
27    }
28    return pow(10.0, x);
29}