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use integer::Integer;
use malachite_base::num::conversion::traits::ExactFrom;
use malachite_base::num::logic::traits::{BitAccess, BitIterable};
use natural::logic::bit_iterable::NaturalBitIterator;
use natural::Natural;
use std::ops::Index;
/// A double-ended iterator over the two's complement bits of the negative of an [`Integer`].
///
/// The forward order is ascending (least-significant first). There may be at most one implicit
/// most-significant `true` bit.
#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
pub struct NegativeBitIterator<'a> {
pub(crate) bits: NaturalBitIterator<'a>,
i: u64,
j: u64,
first_true_index: Option<u64>,
}
impl<'a> Iterator for NegativeBitIterator<'a> {
type Item = bool;
fn next(&mut self) -> Option<bool> {
let previous_i = self.i;
self.bits.next().map(|bit| {
self.i += 1;
if let Some(first_true_index) = self.first_true_index {
if previous_i <= first_true_index {
bit
} else {
!bit
}
} else {
if bit {
self.first_true_index = Some(previous_i);
}
bit
}
})
}
fn size_hint(&self) -> (usize, Option<usize>) {
let significant_bits = usize::exact_from(self.bits.significant_bits);
(significant_bits, Some(significant_bits))
}
}
impl<'a> DoubleEndedIterator for NegativeBitIterator<'a> {
fn next_back(&mut self) -> Option<bool> {
let previous_j = self.j;
self.bits.next_back().map(|bit| {
if self.j != 0 {
self.j -= 1;
}
if self.first_true_index.is_none() {
let mut i = 0;
while !self.bits[i] {
i += 1;
}
self.first_true_index = Some(i);
}
let first_true_index = self.first_true_index.unwrap();
if previous_j <= first_true_index {
bit
} else {
!bit
}
})
}
}
trait SignExtendedBitIterator: DoubleEndedIterator<Item = bool> {
const EXTENSION: bool;
fn needs_sign_extension(&self) -> bool;
fn iterate_forward(&mut self, extension_checked: &mut bool) -> Option<bool> {
let next = self.next();
if next.is_none() {
if *extension_checked {
None
} else {
*extension_checked = true;
if self.needs_sign_extension() {
Some(Self::EXTENSION)
} else {
None
}
}
} else {
next
}
}
fn iterate_backward(&mut self, extension_checked: &mut bool) -> Option<bool> {
if !*extension_checked {
*extension_checked = true;
if self.needs_sign_extension() {
return Some(Self::EXTENSION);
}
}
self.next_back()
}
}
impl<'a> SignExtendedBitIterator for NaturalBitIterator<'a> {
const EXTENSION: bool = false;
fn needs_sign_extension(&self) -> bool {
self[self.significant_bits - 1]
}
}
impl<'a> SignExtendedBitIterator for NegativeBitIterator<'a> {
const EXTENSION: bool = true;
fn needs_sign_extension(&self) -> bool {
let mut i = 0;
while !self.bits[i] {
i += 1;
}
let last_bit_index = self.bits.significant_bits - 1;
if i == last_bit_index {
!self.bits[last_bit_index]
} else {
self.bits[last_bit_index]
}
}
}
/// A double-ended iterator over the twos-complement bits of an [`Integer`].
///
/// The forward order is ascending (least-significant first). The most significant bit corresponds
/// to the sign of the [`Integer`]; `false` for non-negative and `true` for negative. This means
/// that there may be a single most-significant sign-extension bit.
///
/// This `struct` is created by [`BitIterable::bits`]; see its documentation for more.
#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
pub enum IntegerBitIterator<'a> {
Zero,
Positive(NaturalBitIterator<'a>, bool),
Negative(NegativeBitIterator<'a>, bool),
}
impl<'a> Iterator for IntegerBitIterator<'a> {
type Item = bool;
fn next(&mut self) -> Option<bool> {
match *self {
IntegerBitIterator::Zero => None,
IntegerBitIterator::Positive(ref mut bits, ref mut extension_checked) => {
bits.iterate_forward(extension_checked)
}
IntegerBitIterator::Negative(ref mut bits, ref mut extension_checked) => {
bits.iterate_forward(extension_checked)
}
}
}
}
impl<'a> DoubleEndedIterator for IntegerBitIterator<'a> {
fn next_back(&mut self) -> Option<bool> {
match *self {
IntegerBitIterator::Zero => None,
IntegerBitIterator::Positive(ref mut bits, ref mut extension_checked) => {
bits.iterate_backward(extension_checked)
}
IntegerBitIterator::Negative(ref mut bits, ref mut extension_checked) => {
bits.iterate_backward(extension_checked)
}
}
}
}
impl<'a> Index<u64> for IntegerBitIterator<'a> {
type Output = bool;
/// A function to retrieve an [`Integer`]'s two's complement bits by index. Indexing at or
/// above the significant bit count returns `false` or `true` bits, depending on the
/// [`Integer`]'s sign.
///
/// This is equivalent to [`get_bit`](malachite_base::num::logic::traits::BitAccess::get_bit).
///
/// # Examples
/// ```
/// extern crate malachite_base;
///
/// use malachite_base::num::basic::traits::Zero;
/// use malachite_base::num::logic::traits::BitIterable;
/// use malachite_nz::integer::Integer;
///
/// assert_eq!(Integer::ZERO.bits()[0], false);
///
/// // -105 = 10010111 in two's complement
/// let n = Integer::from(-105);
/// let bits = n.bits();
/// assert_eq!(bits[0], true);
/// assert_eq!(bits[1], true);
/// assert_eq!(bits[2], true);
/// assert_eq!(bits[3], false);
/// assert_eq!(bits[4], true);
/// assert_eq!(bits[5], false);
/// assert_eq!(bits[6], false);
/// assert_eq!(bits[7], true);
/// assert_eq!(bits[100], true);
/// ```
fn index(&self, index: u64) -> &bool {
let bit = match *self {
IntegerBitIterator::Zero => false,
IntegerBitIterator::Positive(ref bits, _) => bits.limbs.n.get_bit(index),
IntegerBitIterator::Negative(ref bits, _) => bits.bits.limbs.n.get_bit_neg(index),
};
if bit {
&true
} else {
&false
}
}
}
impl Natural {
// Returns a double-ended iterator over the two's complement bits of the negative of a
// `Natural`. The forward order is ascending, so that less significant bits appear first. There
// may be at most one trailing `true` bit going forward, or leading `true` bit going backward.
// The `Natural` cannot be zero.
//
// # Worst-case complexity
// Constant time and additional memory.
fn negative_bits(&self) -> NegativeBitIterator {
assert_ne!(*self, 0, "Cannot get negative bits of 0.");
let bits = self.bits();
NegativeBitIterator {
bits,
first_true_index: None,
i: 0,
j: bits.significant_bits - 1,
}
}
}
impl<'a> BitIterable for &'a Integer {
type BitIterator = IntegerBitIterator<'a>;
/// Returns a double-ended iterator over the bits of an [`Integer`].
///
/// The forward order is ascending, so that less significant bits appear first. There are no
/// trailing false bits going forward, or leading falses going backward, except for possibly a
/// most-significant sign-extension bit.
///
/// If it's necessary to get a [`Vec`] of all the bits, consider using
/// [`to_bits_asc`](malachite_base::num::logic::traits::BitConvertible::to_bits_asc) or
/// [`to_bits_desc`](malachite_base::num::logic::traits::BitConvertible::to_bits_desc) instead.
///
/// # Worst-case complexity
/// Constant time and additional memory.
///
/// # Examples
/// ```
/// extern crate itertools;
/// extern crate malachite_base;
///
/// use itertools::Itertools;
/// use malachite_base::num::basic::traits::Zero;
/// use malachite_base::num::logic::traits::BitIterable;
/// use malachite_nz::integer::Integer;
///
/// assert_eq!(Integer::ZERO.bits().next(), None);
/// // 105 = 01101001b, with a leading false bit to indicate sign
/// assert_eq!(
/// Integer::from(105).bits().collect_vec(),
/// &[true, false, false, true, false, true, true, false]
/// );
/// // -105 = 10010111 in two's complement, with a leading true bit to indicate sign
/// assert_eq!(
/// Integer::from(-105).bits().collect_vec(),
/// &[true, true, true, false, true, false, false, true]
/// );
///
/// assert_eq!(Integer::ZERO.bits().next_back(), None);
/// // 105 = 01101001b, with a leading false bit to indicate sign
/// assert_eq!(
/// Integer::from(105).bits().rev().collect_vec(),
/// &[false, true, true, false, true, false, false, true]
/// );
/// // -105 = 10010111 in two's complement, with a leading true bit to indicate sign
/// assert_eq!(
/// Integer::from(-105).bits().rev().collect_vec(),
/// &[true, false, false, true, false, true, true, true]
/// );
/// ```
fn bits(self) -> IntegerBitIterator<'a> {
if *self == 0 {
IntegerBitIterator::Zero
} else if self.sign {
IntegerBitIterator::Positive(self.abs.bits(), false)
} else {
IntegerBitIterator::Negative(self.abs.negative_bits(), false)
}
}
}