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Measure theory 1.2.4: require nonempty sets in dist_of_disj_compact_pos#540

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teorth merged 2 commits into
teorth:mainfrom
Chessing234:fix/measure-1-2-1-dist-nonempty
Jul 5, 2026
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Measure theory 1.2.4: require nonempty sets in dist_of_disj_compact_pos#540
teorth merged 2 commits into
teorth:mainfrom
Chessing234:fix/measure-1-2-1-dist-nonempty

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@Chessing234

@Chessing234 Chessing234 commented Jun 24, 2026

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Summary

  • dist_of_disj_compact_pos claimed set_dist E F > 0 for any disjoint compact sets, but fails when either set is empty.

Root cause

set_dist E F = sInf (dist '' (E ×ˢ F)). For E = ∅, the image is empty and sInf ∅ = 0, contradicting > 0. Empty sets are compact and disjoint from anything.

Fix

Require E.Nonempty and F.Nonempty.

Test plan

  • lake build passes

Empty compact sets make set_dist 0 via sInf of an empty set, contradicting > 0.

Co-authored-by: Cursor <cursoragent@cursor.com>
@Chessing234 Chessing234 force-pushed the fix/measure-1-2-1-dist-nonempty branch from cfd93ae to 3a6df65 Compare July 5, 2026 11:24
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Rebased onto current main.

Empty compact sets make set_dist 0; callers now supply Nonempty proofs.
Adds Box.toSet_nonempty_of_IsDyadic for dyadic cube covers.

Co-authored-by: Cursor <cursoragent@cursor.com>
@Chessing234

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Fixed CI: pass Nonempty at both dist_of_disj_compact_pos call sites in Section_1_2_2; added Box.toSet_nonempty_of_IsDyadic.

@teorth teorth merged commit cedd306 into teorth:main Jul 5, 2026
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2 participants