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Rebase infrastructure for pushouts to span diagrams #885
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src/synthetic-homotopy-theory/dependent-universal-property-pushouts.lagda.md
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@EgbertRijke do you have a timeline in mind for finishing this PR? I'm not sure if I should be continuing my development with the old infrastructure, or if it's feasible to start using the shiny new |
Ok let me get it to a decent state so that you can start using it. I’ll try to get it done by the weekend. |
Great! Thanks |
cone-family-dependent-pullback-property P γ = | ||
pair | ||
( precompose-lifts P (horizontal-map-cocone-span s c) γ) | ||
( pair | ||
( precompose-lifts P (vertical-map-cocone-span s c) γ) |
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copattern match
src/synthetic-homotopy-theory/universal-property-pushouts.lagda.md
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I'm converting |
In order to complete this refactoring I'm gonna have to deal with pointed spans as well. Please hang on tight everyone:P |
...and morphisms of pointed arrows too |
Rebase infrastructure for pointed pushouts to pointed span diagrams
I am closing this pull request now, as I am not expecting to make progress on this any time soon. |
In anticipation of #885. The proof of the universal property of coequalizers being preserved by equivalences of coforks got a bit unwieldy, but it should become more conceptual once morphisms and equivalences of cocones under spans are integrated (for now they exist only in the other PR).
Adds strict β-laws for the standard pushouts in a new module `synthetic-homotopy-theory.rewriting-pushouts`. ### Todo - [x] Wait for #885. - [x] ~Refactor postulates of universal properties to be phrased in terms of coherently invertible maps.~ - [x] Add separate file for rewrites `synthetic-homotopy-theory.rewriting-pushouts`.
In this PR I refactor the definitions of spans, morphisms of spans, and equivalences of spans (previously called homotopies of spans), and I will work on a better integration of this infrastructure in the theory of pushouts.
Since this touches upon earlier work of @VojtechStep and @tomdjong, perhaps you two can have a look at this PR when it's ready. (That's not to exclude @fredrik-bakke from also having a look)