// 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 libnum::Float;
/// An iterator of a sequence of evenly spaced floats.
///
/// Iterator element type is `F`.
pub struct Linspace<F> {
start: F,
step: F,
index: usize,
len: usize,
}
impl<F> Iterator for Linspace<F>
where F: Float,
{
type Item = F;
#[inline]
fn next(&mut self) -> Option<F> {
if self.index >= self.len {
None
} else {
// Calculate the value just like numpy.linspace does
let i = self.index;
self.index += 1;
Some(self.start + self.step * F::from(i).unwrap())
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let n = self.len - self.index;
(n, Some(n))
}
}
impl<F> DoubleEndedIterator for Linspace<F>
where F: Float,
{
#[inline]
fn next_back(&mut self) -> Option<F> {
if self.index >= self.len {
None
} else {
// Calculate the value just like numpy.linspace does
self.len -= 1;
let i = self.len;
Some(self.start + self.step * F::from(i).unwrap())
}
}
}
impl<F> ExactSizeIterator for Linspace<F>
where Linspace<F>: Iterator
{}
/// Return an iterator of evenly spaced floats.
///
/// The `Linspace` has `n` elements, where the first
/// element is `a` and the last element is `b`.
///
/// Iterator element type is `F`, where `F` must be
/// either `f32` or `f64`.
#[inline]
pub fn linspace<F>(a: F, b: F, n: usize) -> Linspace<F>
where F: Float
{
let step = if n > 1 {
let nf: F = F::from(n).unwrap();
(b - a) / (nf - F::one())
} else {
F::zero()
};
Linspace {
start: a,
step: step,
index: 0,
len: n,
}
}
/// Return an iterator of floats spaced by `step`, from
/// the half-open interval [a, b).
/// Numerical reasons can result in `b` being included
/// in the result.
///
/// Iterator element type is `F`, where `F` must be
/// either `f32` or `f64`.
#[inline]
pub fn range<F>(a: F, b: F, step: F) -> Linspace<F>
where F: Float
{
let len = b - a;
let steps = F::ceil(len / step);
Linspace {
start: a,
step: step,
len: steps.to_usize().unwrap(),
index: 0,
}
}