This commit adds truncated 2-quotients, groupoid quotients, Eilenberg MacLane spaces, chain complexes, the long exact sequence of homotopy groups, the Freudenthal Suspension Theorem, Whitehead's principle, and the computation of homotopy groups of almost all spheres which are known in HoTT.
Add more theorems about mapping cylinders, fibers, truncated 2-quotient, truncated univalence, pre/postcomposition with an iso in a precategory.
renamings: equiv.refl -> equiv.rfl and equiv_eq <-> equiv_eq'
We move the basic notions of pointed types into init.pointed, to avoid cycles in the import graph. Also adds pointed versions of pi and sigma, with corresponding notation
other changes:
- move result about connectedness of susp to homotopy.susp
- improved definition of circle multiplication
- improved the interface to join
Most notably:
Give le.refl the attribute [refl]. This simplifies tactic proofs in various places.
Redefine the order of trunc_index, and instantiate it as weak order.
Add more about pointed equivalences.
The theorems are mostly about the interaction between pointed equivalences and pointed homotopies
Some of these theorems were missing for (unpointed) equivalences, so I also added them there
more about pointed truncated types, including pointed sets.
also increase the priority of some basic instances that nat/num/pos_num/trunc_index have 0, 1 and + (in both libraries)
also move the notation + for sum into the namespace sum, to (sometimes) avoid overloading with add
Now the file hardly uses eq.rec explicitly anymore.
Also add the fact that horizontal and vertical inverses of paths are equal
Make one more argument explicit in eq.cancel_left and eq.cancel_right (to make it nicer to write 'apply cancel_right p')
Note: this is important. I proved a quite complicated equivalence with calc, by chaining these
equivalences. Now if I want to know the underlying function of this composite equivalence, I have to
unfold all these instances. Without the abstracts, this took 14 seconds, and afterwards, it took 2
seconds.
After this commit we need some more advanced theorems in init/wf, notably function extenstionality.
For this reason I had to refactor the init folder a little bit.
To keep the init folders in both libraries similar, I did the same refactorization in the standard library, even though that was not required for the standard library
