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version 2.080.0

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Function std.range.slide

A fixed-sized sliding window iteration of size windowSize over a source range by a custom stepSize.

auto auto slide(Flag!("withPartial") f = Yes.withPartial, Source) (
  Source source,
  size_t windowSize,
  size_t stepSize = 1
)
if (isForwardRange!Source);

The Source range must be at least a ForwardRange and the windowSize must be greater than zero.

For windowSize = 1 it splits the range into single element groups (aka unflatten) For windowSize = 2 it is similar to zip(source, source.save.dropOne).

Parameters

NameDescription
f Whether the last element has fewer elements than windowSize it should be be ignored (No.withPartial) or added (Yes.withPartial)
source Range from which the slide will be selected
windowSize Sliding window size
stepSize Steps between the windows (by default 1)

Returns

Range of all sliding windows with propagated bi-directionality, forwarding, random access, and slicing.

Note

To avoid performance overhead, bi-directionality is only available when hasSlicing and hasLength are true.

See Also

chunks

Example

Iterate over ranges with windows 

import std.algorithm.comparison : equal;

assert([0, 1, 2, 3].slide(2).equal!equal(
    [[0, 1], [1, 2], [2, 3]]
));

assert(5.iota.slide(3).equal!equal(
    [[0, 1, 2], [1, 2, 3], [2, 3, 4]]
));

Example

set a custom stepsize (default 1) 

import std.algorithm.comparison : equal;

assert(6.iota.slide(1, 2).equal!equal(
    [[0], [2], [4]]
));

assert(6.iota.slide(2, 4).equal!equal(
    [[0, 1], [4, 5]]
));

assert(iota(7).slide(2, 2).equal!equal(
    [[0, 1], [2, 3], [4, 5], [6]]
));

assert(iota(12).slide(2, 4).equal!equal(
    [[0, 1], [4, 5], [8, 9]]
));

Example

Allow the last slide to have fewer elements than windowSize 

import std.algorithm.comparison : equal;

assert(3.iota.slide!(No.withPartial)(4).empty);
assert(3.iota.slide!(Yes.withPartial)(4).equal!equal(
    [[0, 1, 2]]
));

Example

Count all the possible substrings of length 2 

import std.algorithm.iteration : each;

int[dstring] d;
"AGAGA"d.slide!(Yes.withPartial)(2).each!(a => d[a]++);
writeln(d); // ["AG"d:2, "GA"d:2]

Example

withPartial only has an effect if last element in the range doesn't have the full size 

import std.algorithm.comparison : equal;

assert(5.iota.slide!(Yes.withPartial)(3, 4).equal!equal([[0, 1, 2], [4]]));
assert(6.iota.slide!(Yes.withPartial)(3, 4).equal!equal([[0, 1, 2], [4, 5]]));
assert(7.iota.slide!(Yes.withPartial)(3, 4).equal!equal([[0, 1, 2], [4, 5, 6]]));

assert(5.iota.slide!(No.withPartial)(3, 4).equal!equal([[0, 1, 2]]));
assert(6.iota.slide!(No.withPartial)(3, 4).equal!equal([[0, 1, 2]]));
assert(7.iota.slide!(No.withPartial)(3, 4).equal!equal([[0, 1, 2], [4, 5, 6]]));

Authors

Andrei Alexandrescu, David Simcha, Jonathan M Davis, and Jack Stouffer. Credit for some of the ideas in building this module goes to Leonardo Maffi.

License

Boost License 1.0.