use core::f64;

#[inline]
pub fn trunc(x: f64) -> f64 {
    let x1p120 = f64::from_bits(0x4770000000000000); // 0x1p120f === 2 ^ 120

    let mut i: u64 = x.to_bits();
    let mut e: i64 = (i >> 52 & 0x7ff) as i64 - 0x3ff + 12;
    let m: u64;

    if e >= 52 + 12 {
        return x;
    }
    if e < 12 {
        e = 1;
    }
    m = -1i64 as u64 >> e;
    if (i & m) == 0 {
        return x;
    }
    force_eval!(x + x1p120);
    i &= !m;
    f64::from_bits(i)
}

#[cfg(test)]
mod tests {
    #[test]
    fn sanity_check() {
        assert_eq!(super::trunc(1.1), 1.0);
    }
}
