q1tsim 0.3.0

A simple, efficient, quantum computer simulator.
Documentation 
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// Copyright 2019 Q1t BV
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

/// Combine indexes into ranges of indexes
///
/// Combine the index in `nrs` into ranges. Each range is a pair of indices
/// `(first, last)`, with each number in the range `[first..last]` (inclusive)
/// present in `nrs`.
pub fn get_ranges(nrs: &[usize]) -> Vec<(usize, usize)>
{
    let mut snrs = nrs.to_vec();
    snrs.sort();

    let mut first = snrs[0];
    let mut last = first;
    let mut ranges = vec![];
    for &nr in snrs[1..].iter()
    {
        if nr == last+1
        {
            last += 1;
        }
        else
        {
            ranges.push((first, last));
            first = nr;
            last = first;
        }
    }
    ranges.push((first, last));

    ranges
}

/// Reverse bits.
///
/// Return the lowest `nr_bits` bits in `idx` in reverse order. Bits higher
/// than `nr_bits` are lost.
pub fn reverse_bits(idx: u64, nr_bits: usize) -> u64
{
    let mut res = 0;
    let mut sidx = idx;
    for i in 0..nr_bits
    {
        res |= (sidx & 1) << (nr_bits - 1 - i);
        sidx >>= 1;
    }
    res
}

/// Select bits.
///
/// Select the lowest bits from `idx`, and store them at the positions in `bits`.
pub fn shuffle_bits(idx: u64, bits: &[usize]) -> u64
{
    let mut res = 0;
    let mut sidx = idx;
    for i in bits
    {
        res |= (sidx & 1) << i;
        sidx >>= 1;
    }
    res
}

#[cfg(test)]
mod tests
{
    use super::{get_ranges, shuffle_bits, reverse_bits};

    #[test]
    fn test_get_ranges()
    {
        let ranges = get_ranges(&[0, 1, 2, 3, 4, 5, 6]);
        assert_eq!(ranges, vec![(0, 6)]);
        let ranges = get_ranges(&[0, 1, 3, 4, 5, 6]);
        assert_eq!(ranges, vec![(0, 1), (3, 6)]);
        let ranges = get_ranges(&[0, 2, 3, 4, 5, 6]);
        assert_eq!(ranges, vec![(0, 0), (2, 6)]);
        let ranges = get_ranges(&[0, 1, 2, 3, 4, 6]);
        assert_eq!(ranges, vec![(0, 4), (6, 6)]);
        let ranges = get_ranges(&[2, 4, 3, 1, 0, 6]);
        assert_eq!(ranges, vec![(0, 4), (6, 6)]);
        let ranges = get_ranges(&[5, 6, 9, 2, 0, 11]);
        assert_eq!(ranges, vec![(0, 0), (2, 2), (5, 6), (9, 9), (11, 11)]);
    }

    #[test]
    fn test_reverse_bits()
    {
        assert_eq!(reverse_bits(1, 1), 1);
        assert_eq!(reverse_bits(1, 4), 8);
        assert_eq!(reverse_bits(10, 4), 5);
        assert_eq!(reverse_bits(26, 4), 5);
        assert_eq!(reverse_bits(0xfffffffffffffffa, 4), 0x5);
        assert_eq!(reverse_bits(0xffffffffffffaaaa, 32), 0x5555ffff);
        assert_eq!(reverse_bits(0x1ffffffffffffffa, 64), 0x5ffffffffffffff8);
    }

    #[test]
    fn test_shuffle_bits()
    {
        assert_eq!(shuffle_bits(0xc, &[0, 3, 1, 2]), 0x6);
        assert_eq!(shuffle_bits(0xfffffffffffffffa, &[8, 9, 10, 11]), 0xa00);
        assert_eq!(shuffle_bits(0xf555555555555555, &[63, 62, 61, 60]), 0xa000000000000000);
        assert_eq!(shuffle_bits(0x3, &[3, 2, 1, 0]), 0xc);
    }
}