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

use num_traits::Zero;
use std::ops::AddAssign;
use std::ops::Index;
use std::ops::IndexMut;
use std::ops::Mul;

pub trait MatrixMul: Clone + Zero + AddAssign + Mul<Self, Output = Self> {}

impl<T> MatrixMul for T where T: Clone + Zero + AddAssign + Mul<Self, Output = Self> {}

#[derive(Clone, Debug)]
pub struct Matrix<T> {
  nrows: usize,
  ncols: usize,
  elements: Vec<T>,
}

impl<T> Matrix<T> {
  pub fn new(nrows: usize, ncols: usize) -> Matrix<T>
  where
    T: Zero,
  {
    let mut vec = Vec::with_capacity(nrows * ncols);
    for _i in 0..nrows * ncols {
      vec.push(T::zero())
    }
    Matrix {
      nrows,
      ncols,
      elements: vec,
    }
  }
  fn validate(&self) {
    assert_eq!(self.elements.len(), self.nrows * self.ncols)
  }
  pub fn nrows(&self) -> usize {
    self.nrows
  }
  pub fn ncols(&self) -> usize {
    self.ncols
  }
}

impl<T> Index<(usize, usize)> for Matrix<T> {
  type Output = T;
  fn index(&self, key: (usize, usize)) -> &T {
    self.elements.index(key.0 + key.1 * self.ncols)
  }
}

impl<T> IndexMut<(usize, usize)> for Matrix<T> {
  fn index_mut(&mut self, key: (usize, usize)) -> &mut T {
    self.elements.index_mut(key.0 + key.1 * self.ncols)
  }
}

impl<'a, 'b, T> Mul<&'b Matrix<T>> for &'a Matrix<T>
where
  T: Clone + Zero + AddAssign + Mul<T, Output = T>,
{
  type Output = Matrix<T>;
  // n*m * m*p = n*p
  fn mul(self, other: &Matrix<T>) -> Matrix<T> {
    let n = self.nrows;
    let m = self.ncols;
    let p = other.ncols;
    assert_eq!(self.ncols, other.nrows);
    let mut out = Matrix::new(n, p);
    for i in 0..n {
      for j in 0..p {
        for k in 0..m {
          out[(i, j)] += self[(i, k)].clone() * other[(k, j)].clone()
        }
      }
    }
    out.validate();
    out
  }
}

impl<'a, T> Mul<Matrix<T>> for &'a Matrix<T>
where
  T: Clone + Zero + AddAssign + Mul<T, Output = T>,
{
  type Output = Matrix<T>;
  fn mul(self, other: Matrix<T>) -> Matrix<T> {
    self * &other
  }
}
impl<'a, T> Mul<&'a Matrix<T>> for Matrix<T>
where
  T: Clone + Zero + AddAssign + Mul<T, Output = T>,
{
  type Output = Matrix<T>;
  fn mul(self, other: &Matrix<T>) -> Matrix<T> {
    &self * other
  }
}
impl<T> Mul<Matrix<T>> for Matrix<T>
where
  T: Clone + Zero + AddAssign + Mul<T, Output = T>,
{
  type Output = Matrix<T>;
  fn mul(self, other: Matrix<T>) -> Matrix<T> {
    &self * &other
  }
}

// pub struct MatrixPlus<T, const N: usize>(ArrayPlus<ArrayPlus<T, N>, N>);

// #[derive(Clone)]
// // Isomorphic to [T; N+1]
// pub struct ArrayPlus<T, const N: usize> {
//   head: T,
//   tail: [T; N],
// }

// impl<T, const N: usize> ArrayPlus<T, N>
// where
//   for<'a> T: Clone + AddAssign<T>,
// {
//   pub fn sum(&self) -> T {
//     let mut acc = self.head.clone();
//     for elt in self.tail.iter() {
//       acc += elt.clone()
//     }
//     acc
//   }
// }

// pub fn mult_mv<T, const N: usize>(m: MatrixPlus<T, N>, v: ArrayPlus<T, N>) -> ArrayPlus<T, N>
// where
//   T: Mul<T, Output = T> + AddAssign + Clone,
// {
//   let head = &m.0.head * &v;
//   let tail = array_init(|i| (m.0.tail.index(i) * &v).sum());
//   ArrayPlus {
//     head: head.sum(),
//     tail: tail,
//   }
// }

// fn mult_vm<T, const N: usize>(v: ArrayPlus<T, N>, m: MatrixPlus<T, N>) -> MatrixPlus<T, N>
// where
//   T: Mul<T, Output = T> + AddAssign + Clone,
// {
//   let head = m.0.head.clone() * v.head.clone();
//   // let x = m.0.tail[0];
//   let tail: [ArrayPlus<T, N>; N] = array_init(|i| (&m).0.tail[i].clone() * v.tail[i].clone());
//   MatrixPlus(ArrayPlus {
//     head: head,
//     tail: tail,
//   })
// }

// impl<T, const N: usize> Mul for ArrayPlus<T, N>
// where
//   for<'a> &'a T: Mul<&'a T, Output = T>,
// {
//   type Output = ArrayPlus<T, N>;
//   fn mul(self, other: ArrayPlus<T, N>) -> ArrayPlus<T, N> {
//     ArrayPlus {
//       head: &self.head * &other.head,
//       tail: array_init(|i| self.tail.index(i) * other.tail.index(i)),
//     }
//   }
// }

// impl<'a, T, const N: usize> Mul<&'a ArrayPlus<T, N>> for &'a ArrayPlus<T, N>
// where
//   T: Mul<T, Output = T> + Clone,
// {
//   type Output = ArrayPlus<T, N>;
//   fn mul(self, other: &ArrayPlus<T, N>) -> ArrayPlus<T, N> {
//     ArrayPlus {
//       head: self.head.clone() * other.head.clone(),
//       tail: array_init(|i| self.tail.index(i).clone() * other.tail.index(i).clone()),
//     }
//   }
// }

// impl<T, const N: usize> Mul<T> for ArrayPlus<T, N>
// where
//   T: Mul<T, Output = T> + Clone,
// {
//   type Output = ArrayPlus<T, N>;
//   fn mul(self, other: T) -> ArrayPlus<T, N> {
//     ArrayPlus {
//       head: self.head.clone() * other.clone(),
//       tail: array_init(|i| self.tail.index(i).clone() * other.clone()),
//     }
//   }
// }

// // matrix * vector = vector
// pub fn mult_mv<T>(m: Vec<Vec<T>>, v: &Vec<T>) -> Vec<T>
// where
//   for<'a> &'a T: Mul<&'a T, Output = T>,
//   T: std::iter::Sum,
// {
//   m.iter()
//     .map(|r| r.iter().zip(v.iter()).map(|(a, b)| a * b).sum())
//     .collect()
// }