test RandomAccessRange input
import std.algorithm: equal, filter; import std.typecons: Tuple; assert((new int[0]).pairwise.empty); assert([1].pairwise.empty); alias T = Tuple!(int, int); assert(equal([1, 2].pairwise, [T(1, 2)])); assert(equal([1, 2, 3].pairwise, [T(1, 2), T(1, 3), T(2, 3)])); assert(equal([1, 2, 3, 4].pairwise, [T(1, 2), T(1, 3), T(1, 4), T(2, 3), T(2, 4), T(3, 4)]));
test ForwardRange input
import std.algorithm: equal, filter; import std.array : array; auto p = [1].filter!"a < 4".pairwise; assert(p.empty); assert(equal(p.array, [1].pairwise.array)); assert(equal([1, 2, 3, 4].filter!"a < 4".pairwise, [1, 2, 3].pairwise));
http://forum.dlang.org/thread/iqkybajwdzcvdytakgvw@forum.dlang.org#post-vhufbwsqbssyqwfxxbuu:40forum.dlang.org https://issues.dlang.org/show_bug.cgi?id=6788
All Unordered Element Pairs (2-Element Subsets) of a Range.
TODO: Add template parameter to decide if .array should be used internally.