68 lines
2.1 KiB
Rust
68 lines
2.1 KiB
Rust
//! Helper function for random number generator
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//!
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use rand::prelude::*;
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pub trait Rng {
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/// Generate random number between start and end (bot inclusive).
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fn roll_dice(&mut self, min: usize, max: usize) -> usize;
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/// Generate random number between start (inclusive) and end (exclusive).
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fn random_range(&mut self, start: usize, end: usize) -> usize;
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}
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impl Rng for StdRng {
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fn roll_dice(&mut self, min: usize, max: usize) -> usize {
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self.random_range(min, max + 1)
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}
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fn random_range(&mut self, start: usize, end: usize) -> usize {
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let max = (end - start) as u32;
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if max == 0 {
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start
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} else {
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((self.next_u32() % max) + start as u32) as usize
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}
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}
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}
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/// ------------------------------------------------------------------------------------------------
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/// Module unit tests
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/// ------------------------------------------------------------------------------------------------
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#[cfg(test)]
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mod tests {
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use super::Rng;
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use rand::prelude::*;
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#[test]
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fn test_range() {
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let mut rng = StdRng::seed_from_u64(100);
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let x = rng.random_range(5, 8);
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assert!((5..8).contains(&x));
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}
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#[test]
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fn test_range_average() {
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let num_op = 10000;
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let mut rng = StdRng::seed_from_u64(1000);
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let xs: Vec<usize> = (0..num_op).map(|_| rng.random_range(5, 10)).collect();
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let mean = xs.iter().sum::<usize>() / num_op;
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let min = *xs.iter().min().expect("no min");
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let max = *xs.iter().max().expect("no max");
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assert_eq!(mean, 7);
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assert_eq!(min, 5);
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assert_eq!(max, 9);
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}
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#[test]
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fn test_roll_dice() {
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let num_op = 1000;
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let mut rng = StdRng::seed_from_u64(2000);
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let xs: Vec<usize> = (0..num_op).map(|_| rng.roll_dice(1, 7)).collect();
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let mean = xs.iter().sum::<usize>() as f32 / num_op as f32 + 0.5;
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let min = *xs.iter().min().expect("no min");
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let max = *xs.iter().max().expect("no max");
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assert_eq!(mean as usize, 4);
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assert_eq!(min, 1);
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assert_eq!(max, 7);
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}
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}
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