Add canonical morphism helpers to Objects.v #2291
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- Make `unique` tactic global by removing `Local` modifier - Add `map_from_initial` and `map_to_terminal` for canonical morphisms - Add `initial_morphism_unique` and `terminal_morphism_unique` theorems - Proofs use existing `unique` tactic These additions provide cleaner access to unique morphisms from/to initial/terminal objects, as suggested in PR HoTT#2288.
Add canonical morphism helpers + uniqueness lemmas to Objects.v
jdchristensen
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Jun 24, 2025
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Thanks, this looks good!
CharlesCNorton
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Per @jdchristensen's suggestion in HoTT#2288, this PR extracts just ZeroObjects.v for focused review and merging. This provides the foundational infrastructure for zero objects and zero morphisms needed for stable category theory. Changes from original PR based on review feedback: - Uses `IsInitialObject`/`IsTerminalObject` with `::` for instances - Uses new `map_from_initial`/`map_to_terminal` helpers from recently merged PR HoTT#2291 - Follows HoTT style conventions (`rapply`, single-line tactics with `1:`, etc.) - Removed lemmas that now belong in Objects.v - Fixed all import and style issues Some lemmas are retained for backwards compatibility.
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This PR adds helper functions and theorems for working with initial and terminal objects, as suggested by @jdchristensen in #2288.
Changes:
map_from_initialandmap_to_terminalfor canonical morphismsinitial_morphism_uniqueandterminal_morphism_uniquetheoremsuniquetactic global by removingLocalmodifierThese helpers provide cleaner access to the unique morphisms from/to initial/terminal objects, which will be useful for the stable categories formalization and other category theory developments.