fixes issue 6647

[xiop-torres]

Fixes #6647

• Added regression test named test_reduce_pair in libs/core/algorithms/tests/unit/parallel/algorithms
• Test checks correct behavior of hpx::reduce with an accumulator type std::pair<int, int> and input range of type int

Prior versions of HPX failed to compile when using hpx::reduce with a mismatched accumulator type and range type, even if the binary operator supported those combinations. This test ensures that this functionality now works as expected.

[StellarBot]

Can one of the admins verify this patch?

[codacy-production[bot]]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
:white_check_mark: -0.72%	∅

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (15afc8be41b0668584dfafe2d8cf6ffb75dfb715)	244963	210174	85.80%
Head commit (c4d141dcfa62a88d44bcd6e92e84ce86d4ab3b13)	194036 (-50927)	165079 (-45095)	85.08% (-0.72%)

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#6712)	0	0	∅ (not applicable)

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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[hkaiser]

@xiop-torres Thanks for working on this! May I ask you to have a look at the test failure reported? Also, please use English comments, if possible.

[hkaiser]

Closing this as abandoned.