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
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
use core::fmt;
use rand::Rng;

use crate::{ArgumentError, Random};

/// A range constraint for generating random numbers.
///
/// This enum is an input to the [`rand()`] function. See its documentation for
/// more details.
// TODO: Add range variants
#[derive(Debug, Clone, Copy, PartialEq, PartialOrd)]
#[cfg_attr(docsrs, doc(cfg(feature = "random-rand")))]
pub enum Max {
    /// A maximum float bound.
    ///
    /// This bound is exclusive.
    Float(f64),
    /// A maximum integer bound.
    ///
    /// This bound is exclusive.
    Integer(i64),
    /// The default bound when no bound is supplied.
    ///
    /// This bound corresponds to [`Max::Float(1.0)`](Self::Float).
    None,
}

impl Default for Max {
    fn default() -> Self {
        Self::None
    }
}

impl fmt::Display for Max {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::Float(max) => write!(f, "{}", max),
            Self::Integer(max) => write!(f, "{}", max),
            Self::None => f.write_str("Infinity"),
        }
    }
}

/// A generated random number.
///
/// This enum is returned by the [`rand()`] function. See its documentation for
/// more details.
#[derive(Debug, Clone, Copy, PartialEq, PartialOrd)]
#[cfg_attr(docsrs, doc(cfg(feature = "random-rand")))]
pub enum Rand {
    /// A random float.
    ///
    /// A random float is returned from [`rand()`] when given [`Max::Float`] or
    /// [`Max::None`] max constraint.
    Float(f64),
    /// A random integer.
    ///
    /// A random integer is returned from [`rand()`] when given [`Max::Integer`]
    /// max constraint.
    Integer(i64),
}

/// Generate random numbers bounded from below by 0 and above by the given max.
///
/// When `max` is an `i64`, `rand` returns a random integer greater than or
/// equal to zero and less than `max`.
///
/// When `max` is an `f64`, `rand` returns a random floating point number
/// between 0.0 and max, including 0.0 and excluding `max`.
///
/// # Implementation notes
///
/// This function does not yet support range constaints. When support is added,
/// when `max` is a `Range`, `rand` will return a random number where
/// range.member?(number) == true.
///
/// # Examples
///
/// Generate floats from `(0.0..1.0)`:
///
/// ```
/// # use spinoso_random::{rand, ArgumentError, InitializeError, Max, Rand, Random};
/// # #[derive(Debug)]
/// # enum ExampleError { Argument(ArgumentError), Initialize(InitializeError) }
/// # impl From<ArgumentError> for ExampleError { fn from(err: ArgumentError) -> Self { Self::Argument(err) } }
/// # impl From<InitializeError> for ExampleError { fn from(err: InitializeError) -> Self { Self::Initialize(err) } }
/// # fn example() -> Result<(), ExampleError> {
/// let mut random = Random::new()?;
/// let max = Max::None;
/// let rand = rand(&mut random, max)?;
/// assert!(matches!(rand, Rand::Float(x) if x < 1.0));
/// # Ok(())
/// # }
/// # example().unwrap();
/// ```
///
/// Generate random integers:
///
/// ```
/// # use spinoso_random::{rand, ArgumentError, InitializeError, Max, Rand, Random};
/// # #[derive(Debug)]
/// # enum ExampleError { Argument(ArgumentError), Initialize(InitializeError) }
/// # impl From<ArgumentError> for ExampleError { fn from(err: ArgumentError) -> Self { Self::Argument(err) } }
/// # impl From<InitializeError> for ExampleError { fn from(err: InitializeError) -> Self { Self::Initialize(err) } }
/// # fn example() -> Result<(), ExampleError> {
/// let mut random = Random::new()?;
/// let max = Max::Integer(10);
/// let rand = rand(&mut random, max)?;
/// assert!(matches!(rand, Rand::Integer(x) if x < 10));
/// # Ok(())
/// # }
/// # example().unwrap();
/// ```
///
/// # Errors
///
/// When `max` is a negative integer or zero, `rand` returns an
/// [`ArgumentError`].
///
/// When `max` is a negative `f64`, `rand` returns an [`ArgumentError`].
///
/// When `max` is a non-finite `f64`, `rand` returns a domain error
/// [`ArgumentError`].
#[cfg(feature = "random-rand")]
#[cfg_attr(docsrs, doc(cfg(feature = "random-rand")))]
pub fn rand(rng: &mut Random, max: Max) -> Result<Rand, ArgumentError> {
    let constraint = max;
    match constraint {
        Max::Float(max) if !max.is_finite() => {
            // NOTE: MRI returns `Errno::EDOM` exception class.
            Err(ArgumentError::domain_error())
        }
        Max::Float(max) if max < 0.0 => {
            let err = ArgumentError::with_rand_max(constraint);
            Err(err)
        }
        Max::Float(max) if max == 0.0 => {
            let number = rng.next_real();
            Ok(Rand::Float(number))
        }
        Max::Float(max) => {
            let number = rng.gen_range(0.0..max);
            Ok(Rand::Float(number))
        }
        Max::Integer(max) if max < 1 => {
            let err = ArgumentError::with_rand_max(constraint);
            Err(err)
        }
        Max::Integer(max) => {
            let number = rng.gen_range(0..max);
            Ok(Rand::Integer(number))
        }
        Max::None => {
            let number = rng.next_real();
            Ok(Rand::Float(number))
        }
    }
}

#[cfg(test)]
mod tests {
    use super::{rand, Max, Rand};
    use crate::Random;

    #[test]
    fn random_number_domain_error() {
        let mut random = Random::with_seed(33);
        assert!(matches!(rand(&mut random, Max::Float(f64::NAN)), Err(err) if err.is_domain_error()));
        assert!(matches!(rand(&mut random, Max::Float(f64::INFINITY)), Err(err) if err.is_domain_error()));
        assert!(matches!(rand(&mut random, Max::Float(f64::NEG_INFINITY)), Err(err) if err.is_domain_error()));
    }

    #[test]
    fn random_number_in_float_out_float() {
        let mut random = Random::with_seed(33);
        assert!(matches!(rand(&mut random, Max::None), Ok(Rand::Float(num)) if num < 1.0));
        assert!(matches!(
            rand(&mut random, Max::Float(0.5)),
            Ok(Rand::Float(num)) if num < 0.5
        ));
        assert!(matches!(
            rand(&mut random, Max::Float(1.0)),
            Ok(Rand::Float(num)) if num < 1.0
        ));
        assert!(matches!(
            rand(&mut random, Max::Float(9000.63)),
            Ok(Rand::Float(num)) if num < 9000.63
        ));
        assert!(matches!(
            rand(&mut random, Max::Float(0.0)),
            Ok(Rand::Float(num)) if num < 1.0
        ));
        assert!(matches!(
            rand(&mut random, Max::Float(-0.0)),
            Ok(Rand::Float(num)) if num < 1.0
        ));
    }

    #[test]
    fn random_number_in_neg_float_out_err() {
        let mut random = Random::with_seed(33);
        assert!(matches!(
            rand(&mut random, Max::Float(-1.0)), Err(err) if err.message() == "invalid argument"
        ));
    }

    #[test]
    fn random_number_in_neg_integer_out_err() {
        let mut random = Random::with_seed(33);
        assert!(matches!(rand(&mut random, Max::Integer(-1)), Err(err) if err.message() == "invalid argument"));
    }

    #[test]
    fn random_number_in_zero_integer_out_err() {
        let mut random = Random::with_seed(33);
        assert!(matches!(rand(&mut random, Max::Integer(0)), Err(err) if err.message() == "invalid argument"));
    }

    #[test]
    fn random_number_in_pos_integer_out_integer() {
        let mut random = Random::with_seed(33);
        assert!(matches!(rand(&mut random, Max::Integer(1)), Ok(Rand::Integer(0))));
        assert!(matches!(
            rand(&mut random, Max::Integer(9000)),
            Ok(Rand::Integer(ref num)) if (0..9000).contains(num)
        ));
        assert!(matches!(
            rand(&mut random, Max::Integer(i64::MAX)),
            Ok(Rand::Integer(num)) if num >= 0
        ));
    }
}