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axes.rs
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axes.rs
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use crate::{Dimension, Axis, Ix, Ixs};
/// Create a new Axes iterator
pub fn axes_of<'a, D>(d: &'a D, strides: &'a D) -> Axes<'a, D>
where D: Dimension,
{
Axes {
dim: d,
strides: strides,
start: 0,
end: d.ndim(),
}
}
/// An iterator over the length and stride of each axis of an array.
///
/// See [`.axes()`](../struct.ArrayBase.html#method.axes) for more information.
///
/// Iterator element type is `AxisDescription`.
///
/// # Examples
///
/// ```
/// use ndarray::Array3;
/// use ndarray::Axis;
///
/// let a = Array3::<f32>::zeros((3, 5, 4));
///
/// let largest_axis = a.axes()
/// .max_by_key(|ax| ax.len())
/// .unwrap().axis();
/// assert_eq!(largest_axis, Axis(1));
/// ```
#[derive(Debug)]
pub struct Axes<'a, D: 'a> {
dim: &'a D,
strides: &'a D,
start: usize,
end: usize,
}
/// Description of the axis, its length and its stride.
#[derive(Debug)]
pub struct AxisDescription(pub Axis, pub Ix, pub Ixs);
copy_and_clone!(AxisDescription);
impl AxisDescription {
/// Return axis
#[inline(always)]
pub fn axis(self) -> Axis { self.0 }
/// Return length
#[inline(always)]
pub fn len(self) -> Ix { self.1 }
/// Return stride
#[inline(always)]
pub fn stride(self) -> Ixs { self.2 }
}
copy_and_clone!(['a, D] Axes<'a, D>);
impl<'a, D> Iterator for Axes<'a, D>
where D: Dimension,
{
/// Description of the axis, its length and its stride.
type Item = AxisDescription;
fn next(&mut self) -> Option<Self::Item> {
if self.start < self.end {
let i = self.start.post_inc();
Some(AxisDescription(Axis(i), self.dim[i], self.strides[i] as Ixs))
} else {
None
}
}
fn fold<B, F>(self, init: B, f: F) -> B
where
F: FnMut(B, AxisDescription) -> B,
{
(self.start..self.end)
.map(move |i| AxisDescription(Axis(i), self.dim[i], self.strides[i] as isize))
.fold(init, f)
}
fn size_hint(&self) -> (usize, Option<usize>) {
let len = self.end - self.start;
(len, Some(len))
}
}
impl<'a, D> DoubleEndedIterator for Axes<'a, D>
where D: Dimension,
{
fn next_back(&mut self) -> Option<Self::Item> {
if self.start < self.end {
let i = self.end.pre_dec();
Some(AxisDescription(Axis(i), self.dim[i], self.strides[i] as Ixs))
} else {
None
}
}
}
trait IncOps : Copy {
fn post_inc(&mut self) -> Self;
fn post_dec(&mut self) -> Self;
fn pre_dec(&mut self) -> Self;
}
impl IncOps for usize {
#[inline(always)]
fn post_inc(&mut self) -> Self {
let x = *self;
*self += 1;
x
}
#[inline(always)]
fn post_dec(&mut self) -> Self {
let x = *self;
*self -= 1;
x
}
#[inline(always)]
fn pre_dec(&mut self) -> Self {
*self -= 1;
*self
}
}