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Function `std.algorithm.setops.multiwayUnion`

Computes the union of multiple ranges. The input ranges are passed as a range of ranges and each is assumed to be sorted by less. Computation is done lazily, one union element at a time. multiwayUnion(ror) is functionally equivalent to multiwayMerge(ror).uniq.


						
				auto multiwayUnion(alias less, RangeOfRanges)
				(
				

				  RangeOfRanges ror
				

				);

"The output of multiwayUnion has no duplicates even when its inputs contain duplicates."

Parameters

Name	Description
less	Predicate the given ranges are sorted by.
ror	A range of ranges sorted by `less` to compute the intersection for.

Returns

A range of the union of the ranges in ror.

Example

import std.algorithm.comparison : equal;

// sets
double[][] a =
[
    [ 1, 4, 7, 8 ],
    [ 1, 7 ],
    [ 1, 7, 8],
    [ 4 ],
    [ 7 ],
];

auto witness = [1, 4, 7, 8];
assert(equal(multiwayUnion(a), witness));

// multisets
double[][] b =
[
    [ 1, 1, 1, 4, 7, 8 ],
    [ 1, 7 ],
    [ 1, 7, 7, 8],
    [ 4 ],
    [ 7 ],
];
assert(equal(multiwayUnion(b), witness));

double[][] c =
[
    [9, 8, 8, 8, 7, 6],
    [9, 8, 6],
    [9, 8, 5]
];
auto witness2 = [9, 8, 7, 6, 5];
assert(equal(multiwayUnion!"a > b"(c), witness2));

Authors

Andrei Alexandrescu

License

Boost License 1.0.