Add the Barker-Foran cone to the cone catalog #41167
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Among other things, "Self-Dual Cones in Euclidean Spaces" by Barker & Foran gives an example of a rational, self-dual convex cone with five extreme rays in three dimensions. This will soon be included in the cone catalog.
Though it is a name I just made up, the newly minted Barker-Foran cone is a polyhedral self-dual convex cone with five extreme rays in three dimensions. Barker & Foran give it as an example in their paper, which we cite. It is a nice example because asymmetric self-dual cones are hard to come by.
The extreme rays of the Barker-Foran cone look much nicer if we manually align them, but this causes ruff to complain about the one instance where two spaces appear before a negative sign. We add a "noqa" comment to disable that check on that one line.
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Documentation preview for this PR (built with commit 8e2e443; changes) is ready! 🎉 |
cxzhong
reviewed
Nov 14, 2025
| ( zero, one, one), | ||
| (-one, zero, one), | ||
| ( zero, -one, one), | ||
| ( one, -one, one)] # noqa: E221 |
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Why do you add ignore of E221
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I think
ext = [( one, one, one),
( zero, one, one),
(-one, zero, one),
( zero, -one, one),
( one, -one, one)]looks a lot better than
ext = [(one, one, one),
(zero, one, one),
(-one, zero, one),
(zero, -one, one),
(one, -one, one)]but without the "noqa" the lint (ruff) will fail on mine.
I'll change it if it ruins anyone's day, but in this case I think the lint is just being counterproductive.
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This is a handy example of a self-dual (but not symmetric) polyhedral cone given in Self-dual cones in euclidean spaces by Barker & Foran. I mention it in Gaddum's test for symmetric cones, which is freely available.
I've called it the Barker-Foran cone for lack of a better name. The authors define another, related family of cones in the same paper... but the coordinates of their extreme rays aren't rational, so there is no immediate risk of them being added to sage and causing a name clash.