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    #[inline]
    #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
    pub fn scalbn(x: f64, mut n: i32) -> f64 {
        let x1p1023 = f64::from_bits(0x7fe0000000000000); // 0x1p1023 === 2 ^ 1023
        let x1p53 = f64::from_bits(0x4340000000000000); // 0x1p53 === 2 ^ 53
        let x1p_1022 = f64::from_bits(0x0010000000000000); // 0x1p-1022 === 2 ^ (-1022)

        let mut y = x;

        if n > 1023 {
            y *= x1p1023;
            n -= 1023;
            if n > 1023 {
                y *= x1p1023;
                n -= 1023;
                if n > 1023 {
                    n = 1023;
                }
            }
        } else if n < -1022 {
            /* make sure final n < -53 to avoid double
            rounding in the subnormal range */
            y *= x1p_1022 * x1p53;
            n += 1022 - 53;
            if n < -1022 {
                y *= x1p_1022 * x1p53;
                n += 1022 - 53;
                if n < -1022 {
                    n = -1022;
                }
            }
        }
        y * f64::from_bits(((0x3ff + n) as u64) << 52)
    }

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