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

// Copyright 2017 Kyle Mayes
//
// 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.

use super::ratio::{Ratio};
use super::super::{Die, Reroll};

//================================================
// Structs
//================================================

// Die ___________________________________________

impl Die {
    //- Accessors --------------------------------

    /// Returns the smallest possible result of rolling this die.
    pub fn minimum(&self) -> i32 {
        1
    }

    /// Returns the largest possible result of rolling this die.
    pub fn maximum(&self) -> i32 {
        self.0 as i32
    }

    /// Returns the average result of rolling this die.
    pub fn average(&self, reroll: Option<Reroll>) -> Ratio {
        if let Some(reroll) = reroll {
            let mut numerator = 0;
            for result in self.results() {
                if reroll.reroll(result as u32, *self) {
                    numerator += (self.0 + 1) as i128;
                } else {
                    numerator += (result * 2) as i128;
                }
            }
            Ratio::new(numerator, self.0 as i128 * 2)
        } else {
            Ratio::new(self.0 as i128 + 1, 2)
        }
    }

    /// Returns all the possible results of rolling this die.
    pub fn results(&self) -> impl Iterator<Item=i32> {
        self.minimum()..(self.maximum() + 1)
    }

    /// Returns the probabilities of all the possible results of rolling this die.
    pub fn probabilities(&self, reroll: Option<Reroll>) -> Vec<(i32, Ratio)> {
        if let Some(reroll) = reroll {
            let (low, high) = super::numerators(*self, reroll);
            let denominator = self.0.pow(2) as i128;
            let low = Ratio::new(low, denominator);
            let high = Ratio::new(high, denominator);
            self.results().map(|r| {
                let probability = if reroll.reroll(r as u32, *self) { low } else { high };
                (r, probability)
            }).collect()
        } else {
            self.results().map(|r| (r, Ratio::new(1, self.0 as i128))).collect()
        }
    }
}