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Merge pull request #5620 from RazvanN7/Issue_6718

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[WIP] Fix Issue 6718 - nWayUnion => nWayMerge, plus true nWayUnion
merged-on-behalf-of: Andrei Alexandrescu <andralex@users.noreply.github.com>
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The Dlang Bot 2017-07-17 21:08:25 +02:00 • committed by GitHub
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39
std/algorithm/setops.d
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@ -864,6 +864,45 @@ MultiwayMerge!(less, RangeOfRanges) multiwayMerge
alias nWayUnion = multiwayMerge;
alias NWayUnion = MultiwayMerge;
/**
Computes the union of multiple ranges. The input ranges are passed
as a range of ranges and each is assumed to be sorted by $(D
less). Computation is done lazily, one union element at a time.
`multiwayUnion(ror)` is functionally equivalent to `multiwayMerge(ror).uniq`.
Params:
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 intersection of the ranges in `ror`.
See also: $(LREF NWayUnion)
*/
auto multiwayUnion(alias less = "a < b", RangeOfRanges)(RangeOfRanges ror)
{
import std.algorithm.iteration : uniq;
return ror.multiwayMerge.uniq;
}
///
@system unittest
{
import std.algorithm.comparison : equal;
double[][] a =
[
[ 1, 4, 7, 8 ],
[ 1, 7 ],
[ 1, 7, 8],
[ 4 ],
[ 7 ],
];
auto witness = [1, 4, 7, 8];
assert(equal(multiwayUnion(a), witness));
}
/**
Lazily computes the difference of $(D r1) and $(D r2). The two ranges
are assumed to be sorted by $(D less). The element types of the two