boolean_function/
iterator.rs

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
//! Iterators for Boolean functions.

use std::slice::Iter;
use itertools::{Combinations, Itertools};
use num_bigint::BigUint;
use ouroboros::self_referencing;
use crate::{BigBooleanFunction, BooleanFunction, BooleanFunctionImpl, SmallBooleanFunction};

/// Iterator for the successive values of a Boolean function.
///
/// Example:
/// ```rust
/// use boolean_function::BooleanFunctionImpl;
/// use boolean_function::BooleanFunction;
/// use boolean_function::BooleanFunctionIterator;
///
/// let boolean_function = BooleanFunction::from_hex_string_truth_table("1e").unwrap();
/// let mut iterator = boolean_function.iter();
/// assert_eq!(iterator.next(), Some(false));
/// assert_eq!(iterator.next(), Some(true));
/// assert_eq!(iterator.next(), Some(true));
/// assert_eq!(iterator.next(), Some(true));
/// assert_eq!(iterator.next(), Some(true));
/// assert_eq!(iterator.next(), Some(false));
/// assert_eq!(iterator.next(), Some(false));
/// assert_eq!(iterator.next(), Some(false));
/// assert_eq!(iterator.next(), None);
/// ```
pub struct BooleanFunctionIterator {
    current_index: u32,
    max_index: u32,
    inner_bool_func: crate::BooleanFunction,
}

impl BooleanFunctionIterator {
    pub(crate) fn new(bool_func: crate::BooleanFunction) -> Self {
        BooleanFunctionIterator {
            current_index: 0,
            max_index: bool_func.get_max_input_value(),
            inner_bool_func: bool_func,
        }
    }
}

impl Iterator for BooleanFunctionIterator {
    type Item = bool;

    fn next(&mut self) -> Option<Self::Item> {
        if self.current_index > self.max_index {
            // limit of 31 variables
            return None;
        }
        let result = self
            .inner_bool_func
            .compute_cellular_automata_rule(self.current_index);
        self.current_index += 1;
        Some(result)
    }
}

#[self_referencing]
pub struct SmallCloseBalancedFunctionIterator {
    original_truth_table: u64,
    var_count: usize,
    flippable_bit_positions: Vec<usize>,
    flips_count: usize,
    #[borrows(flippable_bit_positions)]
    #[not_covariant]
    combination_generator: Combinations<Iter<'this, usize>>,
}

impl SmallCloseBalancedFunctionIterator {
    pub(crate) fn create(original_function: &SmallBooleanFunction, flippable_bit_positions: Vec<usize>, flips_count: usize) -> Self {
        SmallCloseBalancedFunctionIteratorBuilder {
            original_truth_table: original_function.get_truth_table_u64(),
            var_count: original_function.variables_count(),
            flippable_bit_positions,
            flips_count,
            combination_generator_builder: |flippable_pos| flippable_pos.iter().combinations(flips_count),
        }.build()
    }
}

impl Iterator for SmallCloseBalancedFunctionIterator {
    type Item = SmallBooleanFunction;

    fn next(&mut self) -> Option<Self::Item> {
        let mut new_tt = self.borrow_original_truth_table().clone();
        let var_count = self.borrow_var_count().clone();

        let bits_to_flip = self.with_mut(|fields| {
            fields.combination_generator.next()
        })?;
        for bit_flip_pos in bits_to_flip {
            new_tt ^= 1u64 << bit_flip_pos;
        }

        Some(SmallBooleanFunction::from_truth_table_unchecked(new_tt, var_count))
    }
}

#[self_referencing]
pub struct BigCloseBalancedFunctionIterator {
    original_truth_table: BigUint,
    var_count: usize,
    flippable_bit_positions: Vec<usize>,
    flips_count: usize,
    #[borrows(flippable_bit_positions)]
    #[not_covariant]
    combination_generator: Combinations<Iter<'this, usize>>,
}

impl BigCloseBalancedFunctionIterator {
    pub(crate) fn create(original_function: &BigBooleanFunction, flippable_bit_positions: Vec<usize>, flips_count: usize) -> Self {
        BigCloseBalancedFunctionIteratorBuilder {
            original_truth_table: original_function.biguint_truth_table(),
            var_count: original_function.variables_count(),
            flippable_bit_positions,
            flips_count,
            combination_generator_builder: |flippable_pos| flippable_pos.iter().combinations(flips_count),
        }.build()
    }
}

impl Iterator for BigCloseBalancedFunctionIterator {
    type Item = BigBooleanFunction;

    fn next(&mut self) -> Option<Self::Item> {
        let mut new_tt = self.borrow_original_truth_table().clone();
        let var_count = self.borrow_var_count().clone();

        let bits_to_flip = self.with_mut(|fields| {
            fields.combination_generator.next()
        })?;
        for bit_flip_pos in bits_to_flip {
            let bit_flip_pos = *bit_flip_pos as u64;
            new_tt.set_bit(bit_flip_pos, !new_tt.bit(bit_flip_pos))
        }

        Some(BigBooleanFunction::from_truth_table(new_tt, var_count))
    }
}

pub enum CloseBalancedFunctionIterator {
    Small(SmallCloseBalancedFunctionIterator),
    Big(BigCloseBalancedFunctionIterator),
}

impl Iterator for CloseBalancedFunctionIterator {
    type Item = BooleanFunction;

    fn next(&mut self) -> Option<Self::Item> {
        match self {
            CloseBalancedFunctionIterator::Small(it) => Some(it.next()?.into()),
            CloseBalancedFunctionIterator::Big(it) => Some(it.next()?.into())
        }
    }
}

#[cfg(test)]
mod tests {
    use crate::BooleanFunction;
    use crate::iterator::BooleanFunctionIterator;
    #[test]
    fn test_boolean_function_iterator() {
        let boolean_function = BooleanFunction::from_hex_string_truth_table("1e").unwrap();
        let mut iterator = BooleanFunctionIterator::new(boolean_function);
        assert_eq!(iterator.next(), Some(false));
        assert_eq!(iterator.next(), Some(true));
        assert_eq!(iterator.next(), Some(true));
        assert_eq!(iterator.next(), Some(true));
        assert_eq!(iterator.next(), Some(true));
        assert_eq!(iterator.next(), Some(false));
        assert_eq!(iterator.next(), Some(false));
        assert_eq!(iterator.next(), Some(false));
        assert_eq!(iterator.next(), None);

        let boolean_function =
            BooleanFunction::from_hex_string_truth_table("7969817CC5893BA6AC326E47619F5AD0")
                .unwrap();
        let mut iterator = BooleanFunctionIterator::new(boolean_function);
        assert_eq!(iterator.next(), Some(false));
        assert_eq!(iterator.next(), Some(false));
        assert_eq!(iterator.next(), Some(false));
        assert_eq!(iterator.next(), Some(false));
        assert_eq!(iterator.next(), Some(true));
    }
}