Fix interval division #1804
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Fix interval division #1804
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sim642
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Aug 14, 2025
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| let is_zero v = Ints_t.compare v Ints_t.zero = 0 in | ||
| match y1, y2 with | ||
| | l, u when is_zero l && is_zero u -> (top_of ik,{underflow=false; overflow=false}) | ||
| | l, _ when is_zero l -> div ik (Some (x1,x2)) (Some (Ints_t.one,y2)) | ||
| | _, u when is_zero u -> div ik (Some (x1,x2)) (Some (y1, Ints_t.(neg one))) | ||
| | _ when leq (of_int ik (Ints_t.zero) |> fst) (Some (y1,y2)) -> (top_of ik,{underflow=false; overflow=false}) |
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By the way, I'm not sure why, but the old handling of division by 0 is quite inconsistent (i.e. not monotone in the second argument):
x / [0, 0]returns top (for division by 0).x / [0, 42]delegates tox / [1, 42], which doesn't return top.x / [-42, 0]delegates tox / [-42, -1], which doesn't return top.x / [-42, 42]again returns top (for division by 0).
The new handling consistently returns top in all of the above cases.
Maybe the goal was to imitate the kind of split at 0 which is now part of the general logic in IArith.div?
sim642
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Sep 23, 2025
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Closes #1803.
TODO
leqcheck.