rust-eratos 0.1.1

An implementation of 'Sieve of Eratosthenes' for rust language practice.
Documentation 
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

//! # rust_eratos
//!
//! `rust_eratos` is one of the Sieve of Eratosthenes implementation for rust language practice.

fn get_upper_range_n(n: u32) -> u32 {
    (n as f32).sqrt() as u32 + 1
}

/// Check has prime number below the number given.
///
/// # Examples
/// ```
/// assert_eq!(rust_eratos::has_prime_number_below(0), false);
/// assert_eq!(rust_eratos::has_prime_number_below(1), false);
/// assert_eq!(rust_eratos::has_prime_number_below(2), false);
/// assert_eq!(rust_eratos::has_prime_number_below(3), true);
/// ```
pub fn has_prime_number_below(n: u32) -> bool {
    n > 2
}

/// Check is prime the number given.
///
/// # Examples
/// ```
/// assert_eq!(rust_eratos::is_prime_number(2), true);
/// assert_eq!(rust_eratos::is_prime_number(3), true);
/// assert_eq!(rust_eratos::is_prime_number(11), true);
/// assert_eq!(rust_eratos::is_prime_number(12), false);
/// ```
pub fn is_prime_number(n: u32) -> bool {
    match n {
        0..=1 => false,
        _ => !(2..get_upper_range_n(n)).any(|i| n % i == 0),
    }
}

/// Get prime number count below the number given.
///
/// # Examples
/// ```
/// assert_eq!(rust_eratos::get_prime_number_count_below(2), 0);
/// assert_eq!(rust_eratos::get_prime_number_count_below(3), 1);
/// assert_eq!(rust_eratos::get_prime_number_count_below(11), 4);
/// assert_eq!(rust_eratos::get_prime_number_count_below(12), 5);
/// ```
pub fn get_prime_number_count_below(n: u32) -> usize {
    match n {
        0..=2 => 0,
        _ => (2..n).filter(|i| is_prime_number(*i)).count(),
    }
}

/// Get largest a prime number below the number given.
///
/// # Examples
/// ```
/// assert_eq!(rust_eratos::get_largest_prime_number_below(2), 0);
/// assert_eq!(rust_eratos::get_largest_prime_number_below(3), 2);
/// assert_eq!(rust_eratos::get_largest_prime_number_below(11), 7);
/// assert_eq!(rust_eratos::get_largest_prime_number_below(12), 11);
/// ```
pub fn get_largest_prime_number_below(n: u32) -> u32 {
    match (2..n).rev().find(|i| is_prime_number(*i)) {
        Some(i) => i,
        None => 0,
    }
}

/// Get prime numbers below the number given.
///
/// # Examples
/// ```
/// assert_eq!(rust_eratos::get_prime_numbers_below(2), vec![]);
/// assert_eq!(rust_eratos::get_prime_numbers_below(3), vec![2]);
/// assert_eq!(rust_eratos::get_prime_numbers_below(11), vec![2, 3, 5, 7]);
/// assert_eq!(rust_eratos::get_prime_numbers_below(12), vec![2, 3, 5, 7, 11]);
/// ```
pub fn get_prime_numbers_below(n: u32) -> Vec<u32> {
    let upper_range_n: u32 = get_upper_range_n(n);
    let mut sieve: Vec<u32> = vec![0, 0];
    sieve.append(&mut (2..n).collect());

    for (i, _) in (0..upper_range_n).enumerate() {
        if sieve[i] <= 0 {
            continue;
        }

        let mut next_index = i * i;

        while next_index < sieve.len() {
            sieve[next_index] = 0;
            next_index += i;
        }
    }

    sieve.into_iter().filter(|&element| element > 0).collect()
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn has_prime() {
        assert_eq!(has_prime_number_below(0), false);
        assert_eq!(has_prime_number_below(1), false);
        assert_eq!(has_prime_number_below(2), false);
        assert_eq!(has_prime_number_below(3), true);
        assert_eq!(has_prime_number_below(4), true);
        assert_eq!(has_prime_number_below(5), true);
    }

    #[test]
    fn is_prime() {
        assert_eq!(is_prime_number(0), false);
        assert_eq!(is_prime_number(1), false);
        assert_eq!(is_prime_number(2), true);
        assert_eq!(is_prime_number(3), true);
        assert_eq!(is_prime_number(4), false);
        assert_eq!(is_prime_number(5), true);
        assert_eq!(is_prime_number(6), false);
        assert_eq!(is_prime_number(7), true);
        assert_eq!(is_prime_number(8), false);
        assert_eq!(is_prime_number(9), false);
        assert_eq!(is_prime_number(10), false);
        assert_eq!(is_prime_number(11), true);
        assert_eq!(is_prime_number(12), false);
    }

    #[test]
    fn prime_count_below() {
        assert_eq!(get_prime_number_count_below(0), 0);
        assert_eq!(get_prime_number_count_below(1), 0);
        assert_eq!(get_prime_number_count_below(2), 0);
        assert_eq!(get_prime_number_count_below(3), 1);
        assert_eq!(get_prime_number_count_below(4), 2);
        assert_eq!(get_prime_number_count_below(5), 2);
        assert_eq!(get_prime_number_count_below(6), 3);
        assert_eq!(get_prime_number_count_below(7), 3);
        assert_eq!(get_prime_number_count_below(8), 4);
        assert_eq!(get_prime_number_count_below(9), 4);
        assert_eq!(get_prime_number_count_below(10), 4);
        assert_eq!(get_prime_number_count_below(11), 4);
        assert_eq!(get_prime_number_count_below(12), 5);
        assert_eq!(get_prime_numbers_below(12).len(), 5);
    }

    #[test]
    fn largest_prime_below() {
        assert_eq!(get_largest_prime_number_below(0), 0);
        assert_eq!(get_largest_prime_number_below(1), 0);
        assert_eq!(get_largest_prime_number_below(2), 0);
        assert_eq!(get_largest_prime_number_below(3), 2);
        assert_eq!(get_largest_prime_number_below(4), 3);
        assert_eq!(get_largest_prime_number_below(5), 3);
        assert_eq!(get_largest_prime_number_below(6), 5);
        assert_eq!(get_largest_prime_number_below(7), 5);
        assert_eq!(get_largest_prime_number_below(8), 7);
        assert_eq!(get_largest_prime_number_below(9), 7);
        assert_eq!(get_largest_prime_number_below(10), 7);
        assert_eq!(get_largest_prime_number_below(11), 7);
        assert_eq!(get_largest_prime_number_below(12), 11);

        assert_eq!(get_prime_numbers_below(12).contains(&11), true);
    }

    #[test]
    fn primes_below() {
        assert_eq!(get_prime_numbers_below(0), vec![]);
        assert_eq!(get_prime_numbers_below(1), vec![]);
        assert_eq!(get_prime_numbers_below(2), vec![]);
        assert_eq!(get_prime_numbers_below(3), vec![2]);
        assert_eq!(get_prime_numbers_below(4), vec![2, 3]);
        assert_eq!(get_prime_numbers_below(5), vec![2, 3]);
        assert_eq!(get_prime_numbers_below(6), vec![2, 3, 5]);
        assert_eq!(get_prime_numbers_below(7), vec![2, 3, 5]);
        assert_eq!(get_prime_numbers_below(8), vec![2, 3, 5, 7]);
        assert_eq!(get_prime_numbers_below(9), vec![2, 3, 5, 7]);
        assert_eq!(get_prime_numbers_below(10), vec![2, 3, 5, 7]);
        assert_eq!(get_prime_numbers_below(11), vec![2, 3, 5, 7]);
        assert_eq!(get_prime_numbers_below(12), vec![2, 3, 5, 7, 11]);
    }
}