ndarray 0.13.0

An n-dimensional array for general elements and for numerics. Lightweight array views and slicing; views support chunking and splitting.
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
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203

// Copyright 2014-2016 bluss and ndarray developers.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

use crate::arraytraits::array_out_of_bounds;
use crate::imp_prelude::*;
use crate::NdIndex;

/// Extra indexing methods for array views
///
/// These methods are very similar to regular indexing or calling of the
/// `get`/`get_mut` methods that we can use on any array or array view. The
/// difference here is in the length of lifetime in the resulting reference.
///
/// **Note** that the `ArrayView` (read-only) and `ArrayViewMut` (read-write) differ
/// in how they are allowed implement this trait -- `ArrayView`'s implementation
/// is usual. If you put in a `ArrayView<'a, T, D>` here, you get references
/// `&'a T` out.
///
/// For `ArrayViewMut` to obey the borrowing rules we have to consume the
/// view if we call any of these methods. (The equivalent of reborrow is
/// `.view_mut()` for read-write array views, but if you can use that,
/// then the regular indexing / `get_mut` should suffice, too.)
///
/// ```
/// use ndarray::IndexLonger;
/// use ndarray::ArrayView;
///
/// let data = [0.; 256];
/// let long_life_ref = {
///     // make a 16 × 16 array view
///     let view = ArrayView::from(&data[..]).into_shape((16, 16)).unwrap();
///
///     // index the view and with `IndexLonger`.
///     // Note here that we get a reference with a life that is derived from
///     // `data`, the base data, instead of being derived from the view
///     IndexLonger::index(&view, [0, 1])
/// };
///
/// // view goes out of scope
///
/// assert_eq!(long_life_ref, &0.);
///
/// ```
pub trait IndexLonger<I> {
    /// The type of the reference to the element that is produced, including
    /// its lifetime.
    type Output;
    /// Get a reference of a element through the view.
    ///
    /// This method is like `Index::index` but with a longer lifetime (matching
    /// the array view); which we can only do for the array view and not in the
    /// `Index` trait.
    ///
    /// See also [the `get` method][1] which works for all arrays and array
    /// views.
    ///
    /// [1]: struct.ArrayBase.html#method.get
    ///
    /// **Panics** if index is out of bounds.
    fn index(self, index: I) -> Self::Output;

    /// Get a reference of a element through the view.
    ///
    /// This method is like `ArrayBase::get` but with a longer lifetime (matching
    /// the array view); which we can only do for the array view and not in the
    /// `Index` trait.
    ///
    /// See also [the `get` method][1] (and [`get_mut`][2]) which works for all arrays and array
    /// views.
    ///
    /// [1]: struct.ArrayBase.html#method.get
    /// [2]: struct.ArrayBase.html#method.get_mut
    ///
    /// **Panics** if index is out of bounds.
    fn get(self, index: I) -> Option<Self::Output>;

    /// Get a reference of a element through the view without boundary check
    ///
    /// This method is like `elem` with a longer lifetime (matching the array
    /// view); which we can't do for general arrays.
    ///
    /// See also [the `uget` method][1] which works for all arrays and array
    /// views.
    ///
    /// [1]: struct.ArrayBase.html#method.uget
    ///
    /// **Note:** only unchecked for non-debug builds of ndarray.
    unsafe fn uget(self, index: I) -> Self::Output;
}

impl<'a, 'b, I, A, D> IndexLonger<I> for &'b ArrayView<'a, A, D>
where
    I: NdIndex<D>,
    D: Dimension,
{
    type Output = &'a A;

    /// Get a reference of a element through the view.
    ///
    /// This method is like `Index::index` but with a longer lifetime (matching
    /// the array view); which we can only do for the array view and not in the
    /// `Index` trait.
    ///
    /// See also [the `get` method][1] which works for all arrays and array
    /// views.
    ///
    /// [1]: struct.ArrayBase.html#method.get
    ///
    /// **Panics** if index is out of bounds.
    fn index(self, index: I) -> &'a A {
        debug_bounds_check!(self, index);
        unsafe { &*self.get_ptr(index).unwrap_or_else(|| array_out_of_bounds()) }
    }

    fn get(self, index: I) -> Option<&'a A> {
        unsafe { self.get_ptr(index).map(|ptr| &*ptr) }
    }

    /// Get a reference of a element through the view without boundary check
    ///
    /// This method is like `elem` with a longer lifetime (matching the array
    /// view); which we can't do for general arrays.
    ///
    /// See also [the `uget` method][1] which works for all arrays and array
    /// views.
    ///
    /// [1]: struct.ArrayBase.html#method.uget
    ///
    /// **Note:** only unchecked for non-debug builds of ndarray.
    unsafe fn uget(self, index: I) -> &'a A {
        debug_bounds_check!(self, index);
        &*self.as_ptr().offset(index.index_unchecked(&self.strides))
    }
}

impl<'a, I, A, D> IndexLonger<I> for ArrayViewMut<'a, A, D>
where
    I: NdIndex<D>,
    D: Dimension,
{
    type Output = &'a mut A;

    /// Convert a mutable array view to a mutable reference of a element.
    ///
    /// This method is like `IndexMut::index_mut` but with a longer lifetime
    /// (matching the array view); which we can only do for the array view and
    /// not in the `Index` trait.
    ///
    /// See also [the `get_mut` method][1] which works for all arrays and array
    /// views.
    ///
    /// [1]: struct.ArrayBase.html#method.get_mut
    ///
    /// **Panics** if index is out of bounds.
    fn index(mut self, index: I) -> &'a mut A {
        debug_bounds_check!(self, index);
        unsafe {
            match self.get_ptr_mut(index) {
                Some(ptr) => &mut *ptr,
                None => array_out_of_bounds(),
            }
        }
    }

    /// Convert a mutable array view to a mutable reference of a element, with
    /// checked access.
    ///
    /// See also [the `get_mut` method][1] which works for all arrays and array
    /// views.
    ///
    /// [1]: struct.ArrayBase.html#method.get_mut
    ///
    fn get(mut self, index: I) -> Option<&'a mut A> {
        debug_bounds_check!(self, index);
        unsafe {
            match self.get_ptr_mut(index) {
                Some(ptr) => Some(&mut *ptr),
                None => None,
            }
        }
    }

    /// Convert a mutable array view to a mutable reference of a element without
    /// boundary check.
    ///
    /// See also [the `uget_mut` method][1] which works for all arrays and array
    /// views.
    ///
    /// [1]: struct.ArrayBase.html#method.uget_mut
    ///
    /// **Note:** only unchecked for non-debug builds of ndarray.
    unsafe fn uget(mut self, index: I) -> &'a mut A {
        debug_bounds_check!(self, index);
        &mut *self
            .as_mut_ptr()
            .offset(index.index_unchecked(&self.strides))
    }
}