Opened 2 years ago

Closed 2 years ago

## #30401 closed defect (fixed)

# Unions of subsets of a fixed open set X are not known to be subsets of X

Reported by: | Travis Scrimshaw | Owned by: | |
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Priority: | major | Milestone: | sage-9.2 |

Component: | manifolds | Keywords: | |

Cc: | Eric Gourgoulhon, Michael Jung | Merged in: | |

Authors: | Eric Gourgoulhon | Reviewers: | Travis Scrimshaw |

Report Upstream: | N/A | Work issues: | |

Branch: | bbe5d11 (Commits, GitHub, GitLab) | Commit: | bbe5d11bb921f2ff0e2091d95fe304aaea472dee |

Dependencies: | Stopgaps: |

### Description

See the following:

sage: T = Manifold(2, 'T', start_index=1) sage: U0 = T.open_subset("U0", latex_name="U_0") sage: Uh = T.open_subset("Uh", latex_name="U_h") sage: T.declare_union(U0, Uh) sage: I0h = U0.intersection(Uh, name="I0h", latex_name="I_{0h}") sage: X1 = I0h.open_subset('X1', "X_1") sage: X2 = I0h.open_subset('X2', "X_2") sage: X3 = I0h.open_subset('X3', "X_3") sage: X1.union(X2).is_subset(I0h) False

This means I cannot declare `I0h`

as the union of 3 subsets.

### Change History (5)

### comment:1 Changed 2 years ago by

Branch: | → public/manifolds/union_subsets_30401 |
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Commit: | → bbe5d11bb921f2ff0e2091d95fe304aaea472dee |

### comment:2 Changed 2 years ago by

Authors: | → Eric Gourgoulhon |
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Status: | new → needs_review |

### comment:3 Changed 2 years ago by

Reviewers: | → Travis Scrimshaw |
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Status: | needs_review → positive_review |

Thank you.

### comment:5 Changed 2 years ago by

Branch: | public/manifolds/union_subsets_30401 → bbe5d11bb921f2ff0e2091d95fe304aaea472dee |
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Resolution: | → fixed |

Status: | positive_review → closed |

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New commits:

`Fix bug in union of manifold subsets (Trac #30401)`