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0.7.1  Apr 21, 2023 

0.7.0 

0.6.2  Nov 28, 2021 
0.6.1  Jun 18, 2021 
0.1.17  Dec 26, 2020 
#96 in Math
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47KB
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iternumtools
This is a collection if iterator extensions that make heavy use of number properties. Mostly extending on Range.
LinSpace
LinSpace is an iterator over a range with a fixed number of values all evenly spaced.
use iter_num_tools::lin_space;
// Count from 1.0 up to and including 5.0, with 5 numbers counted in total
let it = lin_space(1.0..=5.0, 5);
assert!(it.eq([1.0, 2.0, 3.0, 4.0, 5.0]));
// Count from 0.0 up to and excluding 5.0, with 5 numbers counted in total
let it = lin_space(0.0..5.0, 5);
assert!(it.eq([0.0, 1.0, 2.0, 3.0, 4.0]));
GridSpace
GridSpace extends on LinSpace.
use iter_num_tools::grid_space;
// count in 2 dimensions (excluding end points),
// from 0.0 up to 1.0 in the x direction with 2 even steps,
// and 0.0 up to 2.0 in the y direction with 4 even steps
let it = grid_space([0.0, 0.0]..[1.0, 2.0], [2, 4]);
assert!(it.eq([
[0.0, 0.0], [0.5, 0.0],
[0.0, 0.5], [0.5, 0.5],
[0.0, 1.0], [0.5, 1.0],
[0.0, 1.5], [0.5, 1.5],
]));
// count in 2 dimensions (including end points),
// from 0.0 up to 1.0 in the x direction,
// and 0.0 up to 2.0 in the y direction with 3 even steps in all directions
let it = grid_space([0.0, 0.0]..=[1.0, 2.0], 3);
assert!(it.eq([
[0.0, 0.0], [0.5, 0.0], [1.0, 0.0],
[0.0, 1.0], [0.5, 1.0], [1.0, 1.0],
[0.0, 2.0], [0.5, 2.0], [1.0, 2.0],
]));
Arange
Arange is similar to LinSpace, but instead of a fixed amount of steps, it steps by a fixed amount.
use iter_num_tools::arange;
let it = arange(0.0..2.0, 0.5);
assert!(it.eq([0.0, 0.5, 1.0, 1.5]));
Note
There is no inclusive version of arange. Consider the following
use iter_num_tools::arange;
let it = arange(0.0..=2.1, 0.5);
We would not expect 2.1 to ever be a value that the iterator will ever meet, but the range suggests it should be included. Therefore, no RangeInclusive implementation is provided.
ArangeGrid
ArangeGrid is the same as GridSpace but for Arange instead of LinSpace.
use iter_num_tools::arange_grid;
// count in 2 dimensions,
// from 0.0 up to 1.0 in the x direction,
// and 0.0 up to 2.0 in the y direction,
// stepping by 0.5 each time
let it = arange_grid([0.0, 0.0]..[1.0, 2.0], 0.5);
assert!(it.eq([
[0.0, 0.0], [0.5, 0.0],
[0.0, 0.5], [0.5, 0.5],
[0.0, 1.0], [0.5, 1.0],
[0.0, 1.5], [0.5, 1.5],
]));
// count in 2 dimensions,
// from 0.0 up to 1.0 in the x direction stepping by 0.5 each time,
// and 0.0 up to 2.0 in the y direction stepping by 1.0 each time
let it = arange_grid([0.0, 0.0]..[1.0, 2.0], [0.5, 1.0]);
assert!(it.eq([
[0.0, 0.0], [0.5, 0.0],
[0.0, 1.0], [0.5, 1.0],
]));
LogSpace
LogSpace is similar to LinSpace, but instead of evenly spaced linear steps, it has evenly spaced logarithmic steps.
use iter_num_tools::log_space;
use itertools::zip_eq;
// From 1.0 up to and including 1000.0, taking 4 logarithmic steps
let it = log_space(1.0..=1000.0, 4);
let expected: [f64; 4] = [1.0, 10.0, 100.0, 1000.0];
assert!(zip_eq(it, expected).all((x, y) (xy).abs() < 1e10));
// From 1.0 up to 1000.0, taking 3 logarithmic steps
let it = log_space(1.0..1000.0, 3);
let expected: [f64; 3] = [1.0, 10.0, 100.0];
assert!(zip_eq(it, expected).all((x, y) (xy).abs() < 1e10));
Alternatives
There is already a project called itertoolsnum
which has quite a few downloads but it
isn't optimised for speed or flexibility.
(try this benchmark for yourself: clone the repo and run cargo bench bench "linspace" allfeatures
)
LinSpace/linspace [1.0, 3.0] x100 (iternumtools)
time: [65.311 ns 65.579 ns 65.898 ns]
LinSpace/linspace [1.0, 3.0] x100 (std)
time: [67.545 ns 67.762 ns 68.047 ns]
LinSpace/linspace [1.0, 3.0] x100 (itertoolsnum)
time: [117.05 ns 117.59 ns 118.23 ns]
fn bench(i: impl Iterator<Item=f64>) > Vec<f64> {
black_box(i.map(x x * 2.0).collect())
}
// first benchmark (fastest)
bench(iter_num_tools::lin_space(1.0..=3.0, 100));
// second benchmark
fn lin_space_std(start: f64, end: f64, steps: usize) > impl Iterator<Item = f64> {
let len = end  start;
let step = len / steps as f64;
(0..=steps).map(move i start + i as f64 * step)
}
bench(lin_space_std(1.0, 3.0, 100));
// third benchmark (slowest)
bench(itertools_num::linspace(1.0, 3.0, 100));
It also does not provide any other utilities. Only linspace
(inclusive) and a 'Cumulative sum' iterator adaptor.
Dependencies
~580KB
~12K SLoC